I can recommend Migadu. Worth it if you already pay for a domain (which you should, imo, to have a portable e-mail address). I pay for the $19 annual plan and find it sufficient, and I love the flexibility of the admin panel.
I considered Migadu, but saw their stance on freespeech and decided not to go with them:
https://www.migadu.com/use/#anti-violence-commitment
"Hate speech" is too vague and highly subjective and just leads to censorship.
While visiting Migadu’s site, seems like a good option for some but new users should definitely read their drawbacks list before committing to it. No 2FA and no encryption. Therefore not a replacement for something like ProtonMail or TutaNota. https://www.migadu.com/procon/
+1 for Migadu! I'd been a paying customer for Protonmail for a few years now but stuff like this had slowly been pushing me away. A few months ago I set up Migadu with my own domain and it's worked without issue ever since. Another plus is that I can finally use my own email clients without having to deal with proton bridge