I found a project called https://github.com/4JX/L5P-Keyboard-RGB, and it worked. The thing is, I don't like how it opens a window to take effect. I don't want to remember my RGB control software exists at all. It should just work, and I think it should feel native. So this project takes the driver and lighting controls of that upstream project and puts all the logic inside a Rust daemon that can run at startup.
From my testing, it's about 8x lighter than the original because the daemon is now decoupled from the GUI, so it uses way fewer resources and remains invisible. I also wanted it to feel native to Linux. I use GNOME, so I made a minimal GUI with GTK4/libadwaita. More GUI's can be made, however.
So the workflow now is to set up the daemon, open the GUI, adjust what you want, and close it. Simple. No RAM bloat or window that needs to stay open.
This project is new, so please feel free to open issues.