I was going to ask if Fastmail went smoother. Bron (CEO) is active in IETF doing the JMAP related stuff and other things, he is responsive to discussion in that place, I felt like they are working to make things more gooder better.

Proton is secure. But it can be very hard to work with. I help seniors who were taken there by their more paranoid friends and associates and now struggle with the GUI and tying it into older mail clients