diff --git a/.github/workflows/build-steps.yml b/.github/workflows/build-steps.yml
index 63f0810ca3..1df1ccaec3 100644
--- a/.github/workflows/build-steps.yml
+++ b/.github/workflows/build-steps.yml
@@ -68,6 +68,10 @@ on:
         type: string
       nametag:
         type: string
+      required_deps:
+        type: string
+      optional_deps:
+        type: string
     secrets:
         PASSED_GITHUB_TOKEN:
           required: false
@@ -102,6 +106,12 @@ jobs:
       ABI_CHECK: ${{inputs.abi_check}}
       ACTIONS_RUNNER_FORCE_ACTIONS_NODE_VERSION: node16
       ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION: true
+      # For CI, sometimes we want to require all dependencies to be present,
+      # except for a select few listed explicitly. This ensures that we don't
+      # accidentally have a situation in which we think we are building
+      # against and testing an optional dependency, but in fact are not.
+      OpenImageIO_REQUIRED_DEPS: ${{inputs.required_deps}}
+      OpenImageIO_OPTIONAL_DEPS: ${{inputs.optional_deps}}
 
     steps:
       - name: Checkout repo
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 87a02695e9..b3bf9e44a5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -239,9 +239,9 @@ jobs:
 
 
   #
-  # Linux Tests
+  # Linux Tests using ASWF-docker containers
   #
-  linux:
+  linux-aswf:
     if: ${{ ! contains(github.ref, 'windows-only') && ! contains(github.ref, 'macos-only') }}
     name: "${{matrix.desc}}"
     uses: ./.github/workflows/build-steps.yml
@@ -273,6 +273,10 @@ jobs:
       ctest_test_timeout: ${{ matrix.ctest_test_timeout }}
       coverage: ${{ matrix.coverage || 0 }}
       sonar: ${{ matrix.sonar || 0 }}
+      # Override required_deps to be 'all' and explicitly list as optional
+      # only the ones we are intentionally not testing for those jobs.
+      required_deps: ${{ matrix.required_deps || 'all' }}
+      optional_deps: ${{ matrix.optional_deps || 'DCMTK;JXL;Libheif;Nuke;OpenCV;openjph;OpenVDB;Qt5;R3DSDK;'}}${{matrix.optional_deps_append}}
     strategy:
       fail-fast: false
       matrix:
@@ -287,6 +291,7 @@ jobs:
             fmt_ver: 10.1.1
             pybind11_ver: v2.10.0
             setenvs: export PUGIXML_VERSION=v1.13
+            optional_deps_append: 'LibRaw;Ptex;Qt6'
           - desc: VFX2023 icc/C++17 py3.10 exr3.1 ocio2.3 qt5.15
             nametag: linux-vfx2023.icc
             runner: ubuntu-latest
@@ -303,6 +308,7 @@ jobs:
                             DISABLE_libuhdr=1
             # For icc, use fp-model precise to eliminate needless LSB errors
             # that make test results differ from other platforms.
+            optional_deps_append: "LibRaw;Ptex;Qt6"
           - desc: VFX2023 icx/C++17 py3.10 exr3.1 ocio2.3 qt5.15
             nametag: linux-vfx2023.icx
             runner: ubuntu-latest
@@ -319,6 +325,7 @@ jobs:
                             UHDR_CMAKE_CXX_COMPILER=g++
             # Building libuhdr with icx results in test failures
             # so we force using gcc/g++.
+            optional_deps_append: "LibRaw;Ptex;Qt6"
           - desc: VFX2024 gcc11/C++17 py3.11 exr3.2 ocio2.3
             nametag: linux-vfx2024
             runner: ubuntu-latest
@@ -330,6 +337,7 @@ jobs:
             pybind11_ver: v2.12.0
             benchmark: 1
             setenvs: export PUGIXML_VERSION=v1.14
+            optional_deps_append: "LibRaw"
           - desc: VFX2024 clang/C++17 py3.11 exr3.2 ocio2.3
             nametag: linux-vfx2024.clang
             runner: ubuntu-latest
@@ -343,6 +351,7 @@ jobs:
             pybind11_ver: v2.12.0
             benchmark: 1
             setenvs: export PUGIXML_VERSION=v1.14
+            optional_deps_append: "LibRaw"
           - desc: VFX2025 gcc11/C++17 py3.11 exr3.3 ocio2.4
             nametag: linux-vfx2025
             runner: ubuntu-latest
@@ -354,6 +363,7 @@ jobs:
             pybind11_ver: v2.13.6
             benchmark: 1
             setenvs: export PUGIXML_VERSION=v1.15
+            optional_deps_append: "openjph;Qt6"
           - desc: VFX2026 gcc14/C++20 py3.13 exr3.4 ocio2.4
             nametag: linux-vfx2026
             runner: ubuntu-latest
@@ -364,6 +374,7 @@ jobs:
             pybind11_ver: v3.0.0
             benchmark: 1
             # setenvs: export 
+            optional_deps_append: "Qt5;Qt6"
           - desc: Sanitizers
             nametag: sanitizer
             runner: ubuntu-latest
@@ -378,6 +389,7 @@ jobs:
                             OIIO_CMAKE_FLAGS="-DSANITIZE=address,undefined -DOIIO_HARDENING=3 -DUSE_PYTHON=0"
                             CTEST_EXCLUSIONS="broken|png-damaged"
                             OpenImageIO_BUILD_LOCAL_DEPS=PNG
+            optional_deps_append: "LibRaw"
 
           # Test ABI stability. `abi_check` is the version or commit that we
           # believe is the current standard against which we don't want to
@@ -397,7 +409,52 @@ jobs:
             abi_check: 9bfcce725a3806a3f70c7e838d9d98d6d95c917a
             setenvs: export OIIO_CMAKE_FLAGS="-DOIIO_BUILD_TOOLS=0 -DOIIO_BUILD_TESTS=0 -DUSE_PYTHON=0"
                             USE_OPENCV=0 USE_FFMPEG=0 USE_PYTHON=0 USE_FREETYPE=0
+            optional_deps_append: "openjph;Qt6"
 
+
+  #
+  # Linux Tests using GHA Ubuntu runners directly
+  #
+  linux-ubuntu:
+    if: ${{ ! contains(github.ref, 'windows-only') && ! contains(github.ref, 'macos-only') }}
+    name: "${{matrix.desc}}"
+    uses: ./.github/workflows/build-steps.yml
+    with:
+      nametag: ${{ matrix.nametag || 'unnamed!' }}
+      runner: ${{ matrix.runner || 'ubuntu-latest' }}
+      container: ${{ matrix.container }}
+      cc_compiler: ${{ matrix.cc_compiler }}
+      cxx_compiler: ${{ matrix.cxx_compiler }}
+      cxx_std: ${{ matrix.cxx_std || '17' }}
+      build_type: ${{ matrix.build_type || 'Release' }}
+      depcmds: ${{ matrix.depcmds }}
+      extra_artifacts: ${{ matrix.extra_artifacts }}
+      fmt_ver: ${{ matrix.fmt_ver }}
+      opencolorio_ver: ${{ matrix.opencolorio_ver }}
+      openexr_ver: ${{ matrix.openexr_ver }}
+      pybind11_ver: ${{ matrix.pybind11_ver }}
+      python_ver: ${{ matrix.python_ver }}
+      setenvs: ${{ matrix.setenvs }}
+      simd: ${{ matrix.simd }}
+      skip_build: ${{ matrix.skip_build }}
+      skip_tests: ${{ matrix.skip_tests }}
+      abi_check: ${{ matrix.abi_check }}
+      benchmark: ${{ matrix.benchmark }}
+      build_docs: ${{ matrix.build_docs }}
+      clang_format: ${{ matrix.clang_format }}
+      generator: ${{ matrix.generator }}
+      ctest_args: ${{ matrix.ctest_args }}
+      ctest_test_timeout: ${{ matrix.ctest_test_timeout }}
+      coverage: ${{ matrix.coverage || 0 }}
+      sonar: ${{ matrix.sonar || 0 }}
+      # Override required_deps to be 'all' and explicitly list as optional
+      # only the ones we are intentionally not testing for those jobs.
+      required_deps: ${{ matrix.required_deps || 'all' }}
+      optional_deps: ${{ matrix.optional_deps || 'CUDAToolkit;DCMTK;JXL;Nuke;OpenGL;openjph;OpenVDB;Ptex;pystring;Qt5;R3DSDK;' }}${{matrix.optional_deps_append}}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
           # Test formatting. This test entry doesn't build at all, it
           # just runs clang-format on everything, and passes if nothing is
           # misformatted. Upon failure, the build artifact will be the full
@@ -440,6 +497,10 @@ jobs:
                             WEBP_VERSION=v1.6.0
                             FREETYPE_VERSION=VER-2-14-0
                             USE_OPENVDB=0
+            # Ensure we are testing all the deps we think we are. We would
+            # like this test to have minimal missing dependencies.
+            required_deps: all
+            optional_deps: 'CUDAToolkit;DCMTK;JXL;Nuke;OpenCV;OpenGL;OpenVDB;R3DSDK'
           - desc: bleeding edge gcc14 C++23 py3.12 OCIO/libtiff/exr-main avx2
             nametag: linux-bleeding-edge
             runner: ubuntu-24.04
@@ -467,6 +528,10 @@ jobs:
                             FREETYPE_VERSION=master
                             QT_VERSION=0 INSTALL_OPENCV=0
                             # The installed OpenVDB has a TLS conflict with Python 3.8
+            # Ensure we are testing all the deps we think we are. We would
+            # like this test to have minimal missing dependencies.
+            required_deps: all
+            optional_deps: 'CUDAToolkit;DCMTK;JXL;Nuke;OpenCV;OpenGL;OpenVDB;R3DSDK'
           - desc: all local builds gcc12 C++17 avx2 exr3.2 ocio2.3
             nametag: linux-local-builds
             runner: ubuntu-22.04
@@ -482,7 +547,6 @@ jobs:
                             PTEX_VERSION=v2.4.2
                             PUGIXML_VERSION=v1.14
                             WEBP_VERSION=v1.4.0
-
           - desc: clang15 C++17 avx2 exr3.1 ocio2.3
             nametag: linux-clang15
             runner: ubuntu-22.04
@@ -597,6 +661,11 @@ jobs:
       ctest_test_timeout: ${{ matrix.ctest_test_timeout || '800' }}
       coverage: ${{ matrix.coverage || 0 }}
       sonar: ${{ matrix.sonar || 0 }}
+      # We're able to use Homebrew to install ALMOST every dependency, so the
+      # only optional ones in our Mac CI tests are commercial things we can't
+      # test in GHA CI.
+      required_deps: ${{ matrix.required_deps || 'all' }}
+      optional_deps: ${{ matrix.optional_deps || 'Nuke;R3DSDK;' }}${{matrix.optional_deps_append}}
     strategy:
       fail-fast: false
       matrix:
@@ -663,6 +732,11 @@ jobs:
       ctest_test_timeout: ${{ matrix.ctest_test_timeout }}
       coverage: ${{ matrix.coverage || 0 }}
       sonar: ${{ matrix.sonar || 0 }}
+      # Windows is a PITA, so we expect very few dependencies to be present or
+      # built. But we would like to add more dependencies and reduce this list
+      # of exceptions in the future.
+      required_deps: ${{ matrix.required_deps || 'all' }}
+      optional_deps: ${{ matrix.optional_deps || 'CUDAToolkit;DCMTK;FFmpeg;GIF;JXL;Libheif;LibRaw;Nuke;OpenCV;OpenGL;OpenJPEG;openjph;OpenCV;OpenVDB;Ptex;pystring;Qt5;Qt6;TBB;R3DSDK;${{matrix.optional_deps_append}}' }}
     strategy:
       fail-fast: false
       matrix:
diff --git a/src/build-scripts/gh-installdeps.bash b/src/build-scripts/gh-installdeps.bash
index 0416c0c276..62d8509084 100755
--- a/src/build-scripts/gh-installdeps.bash
+++ b/src/build-scripts/gh-installdeps.bash
@@ -17,22 +17,28 @@ if [[ "$ASWF_ORG" != ""  ]] ; then
 
     #ls /etc/yum.repos.d
 
-    if [[ "$ASWF_VFXPLATFORM_VERSION" == "2021" || "$ASWF_VFXPLATFORM_VERSION" == "2022" ]] ; then
-        # CentOS 7 based containers need the now-nonexistant centos repo to be
+    # time sudo dnf upgrade --refresh || true
+    time sudo dnf install --nogpgcheck https://mirrors.rpmfusion.org/free/el/rpmfusion-free-release-$(rpm -E %rhel).noarch.rpm -y || true
+
+    if [[ "$ASWF_VFXPLATFORM_VERSION" == "2022" ]] ; then
+        # CentOS 7 based containers need the now-nonexistent centos repo to be
         # excluded or all the subsequent yum install commands will fail.
         yum-config-manager --disable centos-sclo-rh || true
         sed -i 's,^mirrorlist=,#,; s,^#baseurl=http://mirror\.centos\.org/centos/$releasever,baseurl=https://vault.centos.org/7.9.2009,' /etc/yum.repos.d/CentOS-Base.repo
     fi
 
-    sudo yum install -y giflib giflib-devel || true
+    time time sudo yum install -y giflib giflib-devel || true
     if [[ "${USE_OPENCV}" != "0" ]] ; then
-        sudo yum install -y opencv opencv-devel || true
+        time sudo yum install -y opencv opencv-devel || true
     fi
     if [[ "${USE_FFMPEG}" != "0" ]] ; then
-        sudo yum install -y ffmpeg ffmpeg-devel || true
+        time sudo dnf install -y ffmpeg ffmpeg-devel || true
     fi
     if [[ "${USE_FREETYPE:-1}" != "0" ]] ; then
-        sudo yum install -y freetype freetype-devel || true
+        time sudo yum install -y freetype freetype-devel || true
+    fi
+    if [[ "${USE_LIBRAW:-0}" != "0" ]] ; then
+        time sudo yum install -y LibRaw LibRaw-devel || true
     fi
     if [[ "${EXTRA_DEP_PACKAGES}" != "" ]] ; then
         time sudo yum install -y ${EXTRA_DEP_PACKAGES} || true
diff --git a/src/cmake/cuda_macros.cmake b/src/cmake/cuda_macros.cmake
index 29f6c300ce..aadfc45420 100644
--- a/src/cmake/cuda_macros.cmake
+++ b/src/cmake/cuda_macros.cmake
@@ -3,11 +3,11 @@
 # https://github.com/AcademySoftwareFoundation/OpenImageIO
 
 
-set_option (OIIO_USE_CUDA "Include Cuda support if found" OFF)
+set_option (OIIO_USE_CUDA "Include CUDA support if found" OFF)
 set_cache (CUDA_TARGET_ARCH "sm_60" "CUDA GPU architecture (e.g. sm_60)")
 set_cache (CUDAToolkit_ROOT "" "Path to CUDA toolkit")
 
-if (OIIO_USE_CUDA)
+if (OIIO_USE_CUDA AND NOT APPLE)
     set (CUDA_PROPAGATE_HOST_FLAGS ON)
     set (CUDA_VERBOSE_BUILD ${VERBOSE})
     checked_find_package(CUDAToolkit
diff --git a/src/cmake/dependency_utils.cmake b/src/cmake/dependency_utils.cmake
index 02c764fd03..58892a6b43 100644
--- a/src/cmake/dependency_utils.cmake
+++ b/src/cmake/dependency_utils.cmake
@@ -76,7 +76,7 @@ function (dump_matching_variables pattern)
 endfunction ()
 
 
-# Helper: Print a report about missing dependencies and give insructions on
+# Helper: Print a report about missing dependencies and give instructions on
 # how to turn on automatic local dependency building.
 function (print_package_notfound_report)
     message (STATUS)
@@ -286,7 +286,7 @@ macro (checked_find_package pkgname)
     #
     cmake_parse_arguments(_pkg   # prefix
         # noValueKeywords:
-        "REQUIRED;CONFIG;PREFER_CONFIG;DEBUG;NO_RECORD_NOTFOUND;NO_FP_RANGE_CHECK"
+        "REQUIRED;OPTIONAL;CONFIG;PREFER_CONFIG;DEBUG;NO_RECORD_NOTFOUND;NO_FP_RANGE_CHECK"
         # singleValueKeywords:
         "ENABLE;ISDEPOF;VERSION_MIN;VERSION_MAX;RECOMMEND_MIN;RECOMMEND_MIN_REASON;BUILD_LOCAL"
         # multiValueKeywords:
@@ -303,17 +303,24 @@ macro (checked_find_package pkgname)
         set (${pkgname}_FIND_QUIETLY true)
         set (${pkgname_upper}_FIND_QUIETLY true)
     endif ()
-    if ("${pkgname}" IN_LIST ${PROJECT_NAME}_REQUIRED_DEPS OR "ALL" IN_LIST ${PROJECT_NAME}_REQUIRED_DEPS)
+    if ("${pkgname}" IN_LIST ${PROJECT_NAME}_REQUIRED_DEPS
+        OR "ALL" IN_LIST ${PROJECT_NAME}_REQUIRED_DEPS
+        OR "all" IN_LIST ${PROJECT_NAME}_REQUIRED_DEPS)
         set (_pkg_REQUIRED 1)
     endif ()
-    if ("${pkgname}" IN_LIST ${PROJECT_NAME}_OPTIONAL_DEPS OR "ALL" IN_LIST ${PROJECT_NAME}_OPTIONAL_DEPS)
+    if ("${pkgname}" IN_LIST ${PROJECT_NAME}_OPTIONAL_DEPS
+        OR "ALL" IN_LIST ${PROJECT_NAME}_OPTIONAL_DEPS
+        OR "all" IN_LIST ${PROJECT_NAME}_OPTIONAL_DEPS)
         set (_pkg_REQUIRED 0)
+        set (_pkg_OPTIONAL 1)
     endif ()
     # string (TOLOWER "${_pkg_BUILD_LOCAL}" _pkg_BUILD_LOCAL)
     if ("${pkgname}" IN_LIST ${PROJECT_NAME}_BUILD_LOCAL_DEPS
+        OR ${PROJECT_NAME}_BUILD_LOCAL_DEPS STREQUAL "ALL"
         OR ${PROJECT_NAME}_BUILD_LOCAL_DEPS STREQUAL "all")
         set (_pkg_BUILD_LOCAL "always")
     elseif ("${pkgname}" IN_LIST ${PROJECT_NAME}_BUILD_MISSING_DEPS
+            OR ${PROJECT_NAME}_BUILD_MISSING_DEPS STREQUAL "ALL"
             OR ${PROJECT_NAME}_BUILD_MISSING_DEPS STREQUAL "all")
         set_if_not (_pkg_BUILD_LOCAL "missing")
     endif ()
@@ -341,6 +348,11 @@ macro (checked_find_package pkgname)
             set (_quietskip true)
         endif ()
     endif ()
+    if (NOT _enable)
+        set (_pkg_OPTIONAL 1)
+        set (_pkg_REQUIRED 0)
+        message(STATUS "Forcing optional of disabled ${pkgname}")
+    endif ()
     set (_config_status "")
     unset (_${pkgname}_version_range)
     if (_pkg_BUILD_LOCAL AND NOT _pkg_NO_FP_RANGE_CHECK)
@@ -361,7 +373,7 @@ macro (checked_find_package pkgname)
     #
     set (${pkgname}_FOUND FALSE)
     set (${pkgname}_LOCAL_BUILD FALSE)
-    if (_enable OR _pkg_REQUIRED)
+    if (_enable OR (_pkg_REQUIRED AND NOT _pkg_OPTIONAL))
         # Unless instructed not to, try to find the package externally
         # installed.
         if (${pkgname}_FOUND OR ${pkgname_upper}_FOUND OR _pkg_BUILD_LOCAL STREQUAL "always")