> Even better, there is a little-advertised utility called extrepo that has a curated list of external repositories users might want to enable for Debian. To enable the Mozilla repository, for example, a user only needs to install extrepo, run "extrepo enable mozilla" as root (or with sudo), update the package cache, and look for the regular Firefox package. In all, extrepo includes more than 160 external repositories for applications like Docker CE, Signal, and Syncthing. Unfortunately, the extrepo utility does not have a separate "list" command to show the available repositories, though running "extrepo search" with no search parameter will return all of its DEB822-formatted repository entries.
TIL. What a superpower!