Thanks for your reply. I just wanted to follow up to say that first bullet point (roughly) has already bit me. I wanted to have a self-hosted service send me emails via Tuta but because they are totally encrypted and don't offer any bridging (like proton unfortunately does...) I can't set up SMTP at all with Tuta for that use case. Big bummer. Still fuck Proton though, just gotta find something else. I may jump on the train of thought that trying to encrypt email is pointless anyways and just use other channels for that.
And yeah, I have started using my own email domain recently :) wish i had that advice ten years ago!