I migrated from Gmail to Proton a few years ago which already took a large toll on my energy and mental capacity.

I get the feeling that in a few years even the options you suggested will have some sort of downside as well.

Doing a migration dance every few years is getting tiring and unsustainable for me.

Running my own mail server is going to be a losing race to keep me out of spam filters (which you tend find out after you discover that your mails are silently being dropped)

Honestly perhaps we should just migrate from e-mail altogether. The question is to what instead?