Finally I replace my crashing 5700 XT by a 3060 Ti (for gaming).
I'm running Big Sur without acceleration.
I want to use the discrete with Windows and the Intel iGPU with Big Sur.
Before changing EFI files (I'm using AMD config.plist), I'm trying to boot using two cables: HDMI for macOS, DisplayPort for w10.
I updated my BIOS to F20 (for Resize-Bar), but can't see the BIOS using the HDMI (iGPU).
With the F20 BIOS, the iGPU option are limited to auto, enable, disable and can't select initial graphics card.
Any idea?