Currently, my test actions raise a warning No files were found with the provided path: .coverage.*. No artifacts will be uploaded. and then the coverage action fails with Unable to find an artifact with the name: coverage-data.
I checked the coverage docs under https://coverage.readthedocs.io/en/5.5/cmd.html#cmd-combine and it seems that the correct command to create the .coverage.* files is --parallel-mode. Hence I think this line

        session.run("coverage", "run", "--parallel-mode", "-m", "pytest", *session.posargs)

The --parallel worked previously for me. But I could not find the change from --parallel to --parallel-mode in the track changes or documentation of coverage.py.