As someone who has read plenty of discussions about email security (some of them in this very community), including all kind of stuff (from the company groupie to tinfoil-hat conspiracy theories), I have decided to put ~~too many hours~~ some time to discuss the different threat models for email setups, including the basic most people have, the "secure email provider" one (e.g., Protonmail) and the "I use ~~arch~~ PGP manually BTW".
Jokes aside, I hope that it provides an overview comprehensive and - I don't want to say objective, but at least rational - enough so that everyone can draw their own conclusion, while also showing how certain "radical" arguments that I have seen in the past are relatively shortsighted.
The tl;dr is that email is generally not a great solution when talking about security. Depending on your risk profile, using a secure email provider may be the best compromise between realistic security and usability, while if you really have serious security needs, you probably shouldn't use emails, but if you do then a custom setup is your best choice.
Cheers
Since I have found it historically hard to engage on this (broader) subject around here, just yesterday I put together my own thoughts at https://loudwhisper.me/blog/proton-fediverse-burnout/
Personally, I did not see the value of their Mastodon presence, it was write only marketing communication, no engagement with the community anyway. That happened only ever on Reddit, which I think is going to continue being the case.
They push the same info via email newsletter, if someone really wants that stuff.
Either way, the post above covers my take on the whole drama, not just this last small chapter.