Scott yes, but the "problem" with proton is that their encryption is currently less secure than tuta.
This is explained by the fact that the intelligence agencies collect & store everything, including encrypted data, for the quantum computers to decrypt in a few years.
So everything you are sending today with proton is collected & stored, to be decrypted in a few years.
Tuta has already released their quantum resistant encryption earlier this year. Proton said a couple of years ago that they are working on it, but still haven't released anything yet.
[removed reference to a YouTube channel with members who are malicious towards GrapheneOS]
Another "smaller" problem: proton doesn't encrypt email subjects and addresses. Tuta encrypts everything.