Appimages do not have repositories, unlike Flatpaks and Snaps. It’s harder to install or update them since there isn’t a package manager for the Appimages.
I don’t know about Snaps, but Flatpaks are sandboxed, which basically means more security, since apps won’t get access to your system without permission. It’s kind of like Android where apps have to ask for permission to things like camera access, filesystem access, etc.
While I do use Appimages, they remind me of Windows and having to go to websites to download stuff.
Personally, I prefer just installing software with my distro’s package manager and resort to Flatpaks or Appimages when it’s not available in the repos.
In C exit codes are numbers, in the Makefile it says line n° 2014, error 2 probably has some kind of special meaning, you could take a look and search from there.