Also:

• Dockerfile: silence progress in apt commands. For shorter logs.

• to avoid using external Actions (for simple tasks like this).
• perhaps look into how this'd look with podman.
• test --push.
• always run in PRs, but without --push?
  or rather, have it in a test job with no secrets, write right and login.
• maybe merge Dockerfile instructions.
• maybe test on Windows. Also to see if the double-copy workaround is still necessary.