This is an aside, but I also want to give Proton points for their calendar app. I used to use Gsuite and Google calendar and no matter what I did it always opened in agenda mode. The Proton calendar has all the features of Google calendar (as far as I can tell) but their app has an option for default display mode. That brought me incredible joy.
Folks have suggested Proton Mail. It seems pretty good to me!
This is an aside, but I also want to give Proton points for their calendar app. I used to use Gsuite and Google calendar and no matter what I did it always opened in agenda mode. The Proton calendar has all the features of Google calendar (as far as I can tell) but their app has an option for default display mode. That brought me incredible joy.