You mentioned Tutanota, but also Hushmail, Mailfence, Zoho Mail, Mailbox, Posteo, Disroot, etc. I could probably dig up several more honestly without really trying.

I am sorry you feel trapped using Proton. This is the game and moving is time consuming and sometimes complicated. As Proton capitalizes increasing their cost and promoting lock in with their walled garden leaving will have to be a painful and personal choice for you.

I think with something important as email that consumers should take the time, pretending there is not enough time to deal with email is rather silly. I can see how self-defeating your perspective is. I am sorry you have bought into the idea that convenience and security go hand in hand.

I also have issues with using Europe as some panacea to US big tech. While US big tech should be avoided like the plague all their problems are also found in European corporations. There is no magic bullet, but if I had to choose it would be an independent and small provider.

I get the feeling you are an entrenched user who knows better but you are already falling into a sunk cost fallacy situation. Good luck on your endeavors.