Tutanota is a paid service with a calendar app and email client app on Android and iOS. Fdroid availability too. For desktop, AppImage for major Linux distros, including Arch, Debian, Mint, Fedora, etc. I like it so far. My favorite is all the free aliases so that my spam goes somewhere else. My personal email never gets any nonsense.

Clients are Open Source. The service is paid, but I’d rather pay a bit instead of deal with BS. Nothing is free and they have to pay for those servers to run and keep shit in production. It just 3€ a month to get email, use of custom domains, 20GB storage, unlimited calendars, and you can select a family option to add more people for the same price. You can use 3 custom domains. Not sure if you get the domains or just carry them over, but I’d like to know.

Tuta drive is launching in a few months.

I’m also interested in disroot. Check that out. I’ve also tried kolabnow which I thought was okay but didn’t use it to long. I kind of forgot about it.