Well, that's it, I'm never touching Proton again.
As for suggestions: I haven't used Tuta, but I've only heard good things about them. Personally I use mailbox. They have drive and calendar, they're German, and they do/support a lot of cool stuff regarding FOSS. I'm not sure about slop, but from a quick glance I couldn't find a single mention about AI on their website, not even in their job listings. I don't think they have official clients, but they support open standards like SMTP/IMAP, WebDAV etc.
I haven't used their drive and calendar though, only email, since I self-host Nextcloud (if you're into self-hosting, I highly recommend it).