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Jason’s cool photo picker, or jibbly, and was forked from an abandoned project called EHT-sh (acronym meaning unknown) originally made by frederick lumberg, forked and owned by boops_snoops and actively maintained by Xxweeb-lord69xX.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how to build it (which doesn’t work on your distro), but don’t worry because your distro has it prepackaged 1 version out of date and it magically appears on flatpak only after you’ve installed it by other means.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.
As someone who works fairly extensively with all three major platforms… You’re definitely wrong about macOS here. Almost everything on GitHub that works on Linux also works on Mac, aside from GUI applications which are often more OS dependent. The readme pages often just lump Mac and Linux together as they can be pretty similar, especially for things written for interpreted languages (python) where it’s often literally the same.