The question is “What else”. I’ve struggled for years with Fastmail and I’m not competent enough to buy O365.
My second option would be Migadu, though I've not tried them myself yet (I have zero complaints with Purelymail and will use them for as long as they exist).
Another thing I kind of wanted to try is to run a basic mail server on my own hosts, and send the mail through a provider like Purelymail or something, for full control over storage and backups, has anyone here tried that?
I run mine on a Pi4 no problem whatsoever, but I guess a VPS could also be used, although the scamalytics analysis will show it's a server or an IP shared with an anonymising VPN etc. if it's a shared IP on the host.