AMD doesnt have any software for controlling RGB on windows. They don't make graphics cards, they only make the GPU chip that goes onto the card (and the GPU chip doesn't have any LEDs on it).
The LED controllers on the cards are per brand. If you have a Sapphire card, it's Sapphire software that controls the RGB. XFX card -> XFX software, etc.
I have an XFX 9070xt, and it doesnt have any RGB on it. so I haven't had to disable it.
OpenRGB is going to be your best bet for Linux RGB management. Sometimes they dont have every device supported (especially newer ones), so you might not be able to change everything immediately. But it's mostly just a "scan devices, set color values" once it's working.
And the iGPU you can probably disable in the UEFI config.