Huh, a Windows VM might be a brilliant solution to this.
And now I'm wondering - could I maybe use something like Bottles or Wine to install the Windows software that handles Sapphire LEDs? Or would these apps not see the dGPU when virtualised like that?
I would rather disable it on the OS level because I'm slightly paranoid that the dGPU dies at some point and then I can't even access UEFI, because the iGPU is disabled.