If it is still relevant: I was struggling with this issue recently. Available solutions did not work. I did an temporary GitHub action doing a search for the cairo library and found a path not mentioned elsewhere. This may seem like a kind of brute-force but nevertheless it works. I now set this path in my GitHub action file and it works.

Excerpt form my GitHub action YAML file below. I know the logging might be deleted but I kept it for transparency and debugging in case of new problems.

    runs-on: windows-latest
    steps:
      - name: Install Cairo via MSYS2
        uses: msys2/setup-msys2@v2
        with:
          update: true
          install: mingw-w64-x86_64-cairo
      - name: Add MSYS2 Cairo to PATH to make cairocffi libraries like libcairo-2.dll discoverable
        shell: powershell
        # "C:\msys64\mingw64\bin" did not work, try "C:\Program Files\Unity Hub\resources\app.asar.unpacked\node_modules\canvas\build\Release"
        # found using Get-ChildItem -Path C:\ -Filter "*libcairo*.d*" -File -Recurse -ErrorAction SilentlyContinue in Log step
        run: |
          echo "C:\Program Files\Unity Hub\resources\app.asar.unpacked\node_modules\canvas\build\Release" | Out-File -FilePath $env:GITHUB_PATH -Encoding utf8 -Append
          echo "CAIROCFFI_DLL_DIRECTORIES=C:\Program Files\Unity Hub\resources\app.asar.unpacked\node_modules\canvas\build\Release" | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append
      - name: Log environment variable updates
        shell: powershell
        run: |
          Write-Host "GITHUB_PATH: $env:PATH"
          Write-Host "CAIROCFFI_DLL_DIRECTORIES: $env:CAIROCFFI_DLL_DIRECTORIES"

You may refer to the complete yaml here: https://github.com/dornech/utils-msoffice/blob/main/.github/workflows/documentation.yml