I gone through a lot of hosting service providers and unfortunetly cannot find a single one that can be used without running nonfree programs, all of them require loading bulky obfuscated JavaScript apps.
I know of Codeberg Pages for static sites for example, but it is not suitable for any business or professional use.
https://nic.eu.org/ I think would satisfy the simplicity requirement. It’s as barebones as it can be. But you can’t technically register a domain with it. You choose one of the subdomains under
eu.org
and register a subdomain under it.