I think this is ready for review. PRs are:
I don't think it's worthwhile for anybody to look at all of these in detail, and the last two comments on
RFC-809 explain all of the non-mechanical, non-configuration changes (as do the commit messages, which are same across packages). But it'd be good to at least scan those commit messages and spot-check commits other than the big mechanical "run black and isort" ones.
There are also still complaints about MyPy in utils and daf_butler, due to a new version of that appearing on pypi. If I can get that version with conda before I merge, I'll fix the problems here; if I can't, I'll pin the mypy version in the GHA. In any case, I think it's best to consider that distinct from the rest of the ticket, even if it ends up on the same branches.