The worst part about “simple” is defining what that means for the person. Depending on what they mean, there are a lot of different answers.

(And a good chunk of those are just Debian with different branding).

As others have said, EndeavourOS is pretty damn easy too. Personally I’ll stick to Arch for desktop, deb stable for servers/lxc’s, and deb sid for mostly screwing around and sending some reports in so stable can be stable.