Multiple UI instances with PlayerInput & MultiplayerEventSystem

Im trying to setup a local multiplayer game with one UI system for handling general game menu navigation, plus one UI instance for each player to setup their own character.
Its impossible.
Im in since multiple hours now, and all of that feel buggy, conflicting, or non intuitive.
I can't remember all problems I went through.
Im trying without much scripting use, all in Editor should be possible I guess with this new input system to avoid labour.
The doc says some things about PlayerInput, MultiPlayerEventSystem, and InputSystemUIInputModule, but I just can't figure how to setup all these thing to work for my goal.
Do you guys have already tried ?