a transactional SMTP provider, which is almost certainly selling all outgoing email contents for AI training at least if not even more nefarious things.

That’s a big assumption, and that kind of behavior is specifically prohibited in the privacy policy of most, if not all SMTP relay providers, as well as GDPR regulations. If you think they’re violating their own privacy policy and government regulations and doing it anyway, there’s no reason to think Proton isn’t as well, or any other email provider, so that’s kind of a non-starter argument IMO. Plus this only applies to outgoing emails, not incoming. I don’t know about you, but I send about 5-10 outgoing emails a year, there’s not much to be gleaned there. Incoming is what you’d want to protect more than anything.

There’s really no viable way to run your own email server with actual delivery anymore

SMTP relays make IP reputation a complete non-issue. As long as you aren’t sending hundreds of emails a day, there are multiple free options (free tier, subsidized by paying corporate customers who send a lot of emails).

All valid points. The compose setup is nasty, and OIDC definitely needs a major overhaul for sure. I’m hoping those are two issues they address in the near future. I can’t speak to the Android app as I use iOS, I don’t have any complains about that version of their app.

I use OpenCloud with Collabora