I spend a lot of time arguing against Manjaro. That said, Manjaro comes with a GUI package manager that provides access to the AUR.

What software are you using that is not available in the Manjaro repos or AUR? My guess is that the majority of people would never need to install anything more.

I think it is actually quite likely that most people never need more than what is in the Ubuntu repos. However, I am not as confident to stand behind that claim.