I find the yunohost mailserver pretty good ootb

What’s a beginner to do

Well that’s just it; Endeavour is not a beginner distro. It’s not designed to be. Endeavour is Arch with a graphical installer and some modest quality of life improvements for users who are otherwise willing to trawl through the Arch wiki for answers. The welcome app really just seems to be there so that you don’t have to memorize all the commands or set up aliases, etc, if you don’t want to.

So when you ask “am I supposed to X,” the answer is that there really isn’t a set-in-stone workflow to accomplish anything on EOS or Arch; what you’re supposed to do is read the manual, so to speak, and decide for yourself how you want to go about things.

Unlike some other Arch based distros like BlendOS and Manjaro, Endeavour is still very much a DIY distro.

Don’t use GUI package managers, but here, have some GUI package managers.

What GUI package managers are you referring to? EOS doesn’t supply any.

AFAICT they made something more confusing than Arch, not less.

If I’m not mistaken, this is all stuff you should also be doing on Arch. The single difference is that EOS provides a button in their “Welcome” app that will helpfully run a command for you in a terminal for some of these tasks.