What's wrong with Proton Mail? I have heard it being suggested as an alternative to Gmail, but don't know anything beyond it.
e.g.
https://www.404media.co/manifestos-fear-and-loser-thinking-i...
https://www.gadgetreview.com/ai-or-unemployment-proton-is-re...
I started to be wary when they got into Cryptocurrency https://proton.me/blog/proton-wallet-launch
For Proton Mail specifically, they are now pushing AI features, e.g. https://proton.me/blog/proton-scribe-writing-assistant.
The 404 media link is in a comment unthread, reading it does give me the impression that I should avoid the company.