Try workaround described in swift-actions/setup-swift#684 (comment)

Author: mdepinet

.github/workflows/check.yaml

@@ -6,14 +6,10 @@ on:
 
 jobs:
   check:
-    runs-on: macos-latest
+    runs-on: macos-15  # As of Oct 16, 2024 this is actually later than "latest" and consequently has Swift 6.0.0
     steps:
       - uses: actions/checkout@v4
 
-      - uses: swift-actions/[email protected]  # GH actions currently only have Swift 5.10.0
-        with:
-          swift-version: "6.0.0"
-
       - name: format
         run: swiftformat . --lint --reporter github-actions-log