Yes. There is controversy about the CEO. But mostly for me: is security theater. And in don't trust them. Email will never work as a secure communication layer. Stop pretending it will. There a reasons which is tied to the protocol level, that make pgp non sufficient. There are also the pgp technology it self (no forward secrecy, no deniability, key management etc). Then there is the obvious fact about an email from proton to gmail, and 99% of other email providers, simply not being secure/encrypted. So you buy a privacy tool, which neglects to tell you: we actually don't provide privacy at all - unless you treat proton emails as proton chat - strictly proton to proton.. at which point youd be better of with e g signal.

If you insist: mailfence.org allows you to upload and control you own pgp keys. That's interoprational with proton. Simarly priced i think, also Schweiz, and a bit more honest and strict imap (no bridge). But honestly.. stop treating email as secure.