https://www.tuta.com/ Is the only other major player I am aware of— although they have a significantly smaller product lineup than Proton, and aren’t as viable an alternative to Google for those who want a fully integrated suite. Tuta does Mail and Calendar fairly well, cant speak to their drive product.

The other option is self hosting.

For the kind of end-to-end encrypted support they advertise? Tuta is the only one I know of.

Email more broadly? I can heartily recommend Fastmail.

I don't really send anything sensitive over email if I can help it. Signal is a much better choice.

Andy Yen himself mentions "Tuta": https://tuta.com/en/secure-email