Paul Menzel wrote:
Do you have any ideas regarding the USB issues with a dedicated GPU device with integrated USB Type-C port plugged in ?
Maybe multiple xHCI controllers trip up the SeaBIOS xHCI driver?
Two tests would be useful, the latter can be performed by anyone:
1. Connect the keyboard to the graphics card USB port (try with and without a hub)
2. On any mainboard with coreboot and SeaBIOS (maybe even qemu), connect multiple xHCI host controllers (PCIe cards) and see what the logs say.