I'm not the poster you're replying to, but i did the same thing and use Purelymail (and their web interface, which i think is open-source)
it's a very cheap no-nonsense service, i recommend it
Also not the poster you're replying to, but I get email with ProtonVPN, which I've linked to my domain.
I'm not without my questions about them as a company, but Google are getting beyond a joke.
Full migration away is coming with next phone upgrade.
+1 for Purelymail. Most things that appear to be too good to be true are not true. Purelymail is the real deal.
Over the years I've recommended Migadu and still do. Affordable and reliable with usage based pricing.
As for the email client I personally prefer Thunderbird on PC and FairEmail on Android.
https://migadu.com/
https://email.faircode.eu/