F-droid also has very different goals and lives in a much smaller and in some ways much saner ecosystem.

Yes, but pypi has 4 millions release to check, and the scientific and machine learning wheels are very hard to compile (scipy contains c, fortran and assembly code, and must be compiled to mac, linux and windows).

Providing a build env for that would make it prohibitively complicated and expensive, and basically would mirror github CI.

That's the reason continuum is making money: they sell a python package distribution channel that is checked and locked.

F-Droid is infamously known for taking weeks to build a new version of any app.