Hoe do you self host a nix package repo & install nix packages from 3rd party repos? Is this even possible.
Other package managers allow you to install packages from 3rd party repos such as Flatpaks, apt, F-Droid, Scoop, Winget.
And is there any known 3rd party nix package repos?
Nix doesn’t really have “repos” like other distros. There is nix source and there are binary caches.
To use source, you import it. I think that is easiest with flakes, but there are multiple ways to do it.
If you want to self host the binary cache, you’ll want to look at using a substituter. There are several ways to host a cache as well.