Flathub aims to be the place to get and distribute apps for Linux. It is powered by Flatpak which allows Flathub apps to run on almost any Linux distribution.
How does it stack up against traditional package management and others like AUR and Nix?
It likes to not see the whole file structure; for instance I found the Flatpak version of Steam to be unusable because it wouldn’t see anywhere I wanted to put my games library. That needs to be fixed.
That has been fixed with the introduction of Portals: https://docs.flatpak.org/en/latest/portal-api-reference.html