I stumbled upon a review of
Purelymail here:
https://rolisz.ro/2020/04/11/moving-away-from-gmail/
Still in Beta, but sounds like they are making progress. It is a one-man show run by Scott Johnson. They now have a flat price tier of only $10 a year in addition to their unusual "Advanced Pricing" that charges you for actual resource usage. Has to be one of the least expensive options for domain email going.