I find that Python is significantly easier to write and maintain when it's statically typed via mypy. It's fairly easy to add types incrementally. Here's a good post on how Zulip started using it (also a Django project, albeit larger than Bookwyrm) talking about benefits and approaches to migrating.

The steps for this would probably look like:

• Get mypy running on the codebase without annotations, using # type: ignore where needed
• Add mypy to test script / CI
• Require type annotations, but exempt all existing code on a per-module basis. This will require new modules to be typed, without requiring huge changes all at once.
• Slowly, over time, add type annotations for existing modules, and remove the exemptions as we do so.

I'd be happy to drive this if it's something people are open to.