Yeah, I'll use Tuta if I want an email service that I can't use IMAP with, and then I still have to find a replacement for the 95% of other services Google Workplace offers.

I use Tuta, quite happy with it. The app is available on F-Droid, and I can sync contacts to my phone, which is very convenient.

Sure, it does not have everything Google has, but I mainly need Mail and Calendar, and for this it’s great. They are also working on a Drive.