Hi @RFluff. I am one of the maintainers of SuperCollider. I’m sorry this was a frustrating experience for you.
We have a very handy git cheat sheet which has tips for working with submodules and for working with git in general: https://github.com/supercollider/supercollider/wiki/git-cheat-sheet#working-with-submodules. In fact it provides a description of and solution to the problem you are describing here, because it turns out many developers also struggle with understanding and using submodules.
This is linked from our developer reference, here: https://github.com/supercollider/supercollider/wiki#developer-reference. I would encourage you to read those articles if you are still interested in contributing to SuperCollider, they contain a lot of advice and documentation that has been accumulated over the years. Feel free to contribute your own information as well if there is anything you find missing!
Git is a complex tool, and it would take much longer than an evening to learn every aspect of the submodule system, let alone the entire tool. We have tried to document the common workflows and problems new and experienced contributors have encountered.
If you want immediate help with a development problem, it might be a good idea to join our Slack space and leave a message in the #dev channel! People are often quick to respond there.