Remove Python 3.8 support once EOL

[Technologicat]

Python 3.8 reaches EOL in October 2024.

Purge its version-specific quirks from the codebase, if any remain. This ticket is mainly a reminder to self to check this before release.

[Technologicat]

Maybe better to leave 3.8 support in for now, since it shouldn't hurt anything - we can remove it in the next release.