Could be, but I don’t know anything about it! Of course there are distributions based on Arch (like SteamOS) and Gentoo (like ChromeOS) that can be perfectly usable for beginners to the Linux world. In general, though, I’d probably recommend using something common, and not using a rolling release distro as a beginner.

Realistically, though, the distro probably doesn’t matter too much for a first install, as long as you pick one where you get a reasonably well featured desktop environment out of the box. Beyond that the biggest difference between most distros is the package repository and package manager… You’ll probably pick up pretty quickly that you need to use dnf or yum or whatever on something like Fedora vs the apt suite on something like mint. It’s also kind of a time honoured tradition to do some distro hopping when dipping your toes in Linux, which I think is a good idea because you’ll learn about some of the different things that are available :). It’s not even too big of a deal if you preserve your home partition between installs (have a backup if you mess this up, though).

I’ve been in Unix land pretty much my whole life and I’ve been on Gentoo and NixOS for a long time so I’m not totally up to date on the beginner friendly distros either haha. Frankly, as long as you pick something with a short and simple install process (which most distros have) you’ll be fine in my opinion.

Yes. Assuming they aren't terrified of the command line. It's actually quite easy. Updating everything on the system just requires you to open a terminal and type in "yay". As far as Arch goes it is one of the simpler ones.

Endeavour is very terminal centric. I’d recommend first something with an app gui

I wouldn't say so - it requires terminal use.