ALL email is insecure for an international state level actor (such as the federal US government) to hack, and this includes proton.  This being said, self-hosted is much stronger resistance than services like proton, because proton can much more easily access the data and has a history of doing so for thousands of people.  You would find this article very useful:
https://simplifiedprivacy.com/email-basics/

We can’t go back to 1985.  But you can still get laid and drive fast cars because of all the extra time you’ll be saving by having us setup your email for you. =)