I've been transitioning to Linux recently and have been forced to use github a lot when I hadn't much before. Here is my assessment.
Every github project is named something like dbutils, Jason's cool photo picker, or jibbly, and was forked from an abandoned project called EHT-sh (acronym meaning unknown) originally made by frederick lumberg, forked and owned by boops_snoops and actively maintained by Xxweeb-lord69xX.
There are either 3 lines of documentation and no releases page, or a 15 page long readme with weekly releases for the last 15 years and nothing in between. It is either for linux, windows, or both. If it's for windows, they will not specify what platforms it runs on. If it's for Linux, there's a 50% chance there are no releases and 2 lines of commands showing how to build it (which doesn't work on your distro), but don't worry because your distro has it prepackaged 1 version out of date and it magically appears on flatpak only after you've installed it by other means. Everything is written in python2. It is illegal to release anything for Mac OS on github.
Well personally if a package is not on aur I first check if there's an appimage available, or if there's a flatpak. If neither exist, I generally make a package for myself.
It sounds intimidating, but for most software the package description is just gonna be a single file of maybe 10-15 lines. It's a useful skill to learn and there's lots of tutorials explaining how to get into it, as well as the arch wiki serving as documentation. Not to mention, every aur or arch package can be looked at as an example, just click the "view PKGBUILD" link on the side on the package view. You can even simply download an existing package with git clone and just change some bits.
Alternatively you can just make it locally and use it like that, i.e. just run make without install.