diff --git a/.github/docker/ubuntu-20.04.Dockerfile b/.github/docker/ubuntu-20.04.Dockerfile
index 8869303b7d..9de50673fa 100644
--- a/.github/docker/ubuntu-20.04.Dockerfile
+++ b/.github/docker/ubuntu-20.04.Dockerfile
@@ -11,10 +11,10 @@
 FROM registry.hub.docker.com/library/ubuntu@sha256:f2034e7195f61334e6caff6ecf2e965f92d11e888309065da85ff50c617732b8
 
 # Set environment variables
-ENV OS ubuntu
-ENV OS_VER 20.04
-ENV NOTTY 1
-ENV DEBIAN_FRONTEND noninteractive
+ENV OS=ubuntu
+ENV OS_VER=20.04
+ENV NOTTY=1
+ENV DEBIAN_FRONTEND=noninteractive
 
 # Base development packages
 ARG BASE_DEPS="\
@@ -65,7 +65,7 @@ RUN mkdir -p --mode 777 /opt/umf/
 COPY third_party/requirements.txt /opt/umf/requirements.txt
 
 # Add a new (non-root) 'test_user'
-ENV USER test_user
-ENV USERPASS pass
+ENV USER=test_user
+ENV USERPASS=pass
 RUN useradd -m -u 1001 "${USER}" -g sudo -p "$(mkpasswd ${USERPASS})"
 USER test_user
diff --git a/.github/docker/ubuntu-22.04.Dockerfile b/.github/docker/ubuntu-22.04.Dockerfile
index 915d92c26f..748a2d544c 100644
--- a/.github/docker/ubuntu-22.04.Dockerfile
+++ b/.github/docker/ubuntu-22.04.Dockerfile
@@ -11,14 +11,13 @@
 FROM registry.hub.docker.com/library/ubuntu@sha256:e6173d4dc55e76b87c4af8db8821b1feae4146dd47341e4d431118c7dd060a74
 
 # Set environment variables
-ENV OS ubuntu
-ENV OS_VER 22.04
-ENV NOTTY 1
-ENV DEBIAN_FRONTEND noninteractive
+ENV OS=ubuntu
+ENV OS_VER=22.04
+ENV NOTTY=1
+ENV DEBIAN_FRONTEND=noninteractive
 
 # Base development packages
-# It seems that libtool is not directly needed
-# but it is still required when Building UMF
+# 'libtool' is required when hwloc is statically linked and built from source
 ARG BASE_DEPS="\
 	build-essential \
 	cmake \
@@ -37,10 +36,13 @@ ARG TEST_DEPS="\
 	valgrind"
 
 # Miscellaneous for our builds/CI (optional)
+# 'pkg-config' is added only on one Ubuntu image to test both:
+# 	find_library and pkg-config methods of finding libraries.
 ARG MISC_DEPS="\
 	automake \
 	clang \
 	lcov \
+	pkg-config \
 	python3-pip \
 	sudo \
 	whois"
@@ -63,7 +65,7 @@ COPY third_party/requirements.txt /opt/umf/requirements.txt
 RUN pip3 install --no-cache-dir -r /opt/umf/requirements.txt
 
 # Add a new (non-root) 'test_user'
-ENV USER test_user
-ENV USERPASS pass
+ENV USER=test_user
+ENV USERPASS=pass
 RUN useradd -m -u 1001 "${USER}" -g sudo -p "$(mkpasswd ${USERPASS})"
 USER test_user
diff --git a/.github/docker/ubuntu-24.04.Dockerfile b/.github/docker/ubuntu-24.04.Dockerfile
index e56338ab95..21e7f01602 100644
--- a/.github/docker/ubuntu-24.04.Dockerfile
+++ b/.github/docker/ubuntu-24.04.Dockerfile
@@ -11,16 +11,18 @@
 FROM registry.hub.docker.com/library/ubuntu@sha256:72297848456d5d37d1262630108ab308d3e9ec7ed1c3286a32fe09856619a782
 
 # Set environment variables
-ENV OS ubuntu
-ENV OS_VER 24.04
-ENV NOTTY 1
-ENV DEBIAN_FRONTEND noninteractive
+ENV OS=ubuntu
+ENV OS_VER=24.04
+ENV NOTTY=1
+ENV DEBIAN_FRONTEND=noninteractive
 
 # Base development packages
+# 'libtool' is required when hwloc is statically linked and built from source
 ARG BASE_DEPS="\
 	build-essential \
 	cmake \
 	git \
+	libtool \
 	wget"
 
 # UMF's dependencies
@@ -60,7 +62,7 @@ COPY third_party/requirements.txt /opt/umf/requirements.txt
 RUN pip3 install --no-cache-dir --break-system-packages -r /opt/umf/requirements.txt
 
 # Add a new (non-root) 'test_user'
-ENV USER test_user
-ENV USERPASS pass
+ENV USER=test_user
+ENV USERPASS=pass
 RUN useradd -m "${USER}" -g sudo -p "$(mkpasswd ${USERPASS})"
 USER test_user