I have been a very happy customer for several years. I even really like their web interface.
The list below is of the format: Provider name (Hosting Location):
1. Mailbox.org (Germany)
2. Runbox.com (Norway)
3. Mailfence (Belgium)
4. Migadu (France; company is in Switzerland)
5. Inbox.eu (Latvia)
6. Mxroute (USA)
I prefer that over proprietary solutions.
I think you can get tutanota to interop with Proton if you use Proton's relay.
https://www.swissinfo.ch/eng/proton-wins-appeal-in-swiss-cou...
Not sure if you followed that, but they fought it tooth.and nail, and were forced to do that legally in the meanwhile- but WON The fight finally, and can't be forced to log via legal mechanisms as the authorities attempted
their monthly for allowing custom domains is $10
i was looking for fastmail (which i forgot the name why i posted) which costs $5
If you're paying for iCloud, Apple also supports custom domains and this integrates with Apple's mail apps, allowing you to send mail as any of the hosted accounts without additional configuration.