another solution, Leaving the IGPU disabled in the Bios, try to reinstall AMD Chipset Drivers 5.11.02.217 WHQL to see if this would not clear the missing PCI driver error in your device manager.
If you go to Advanced\AMD CBS\NBIO Common Options\GFX Configuration there should also be an option to disable the integrated graphics controller. On old Bios before July 2023 this was the only way to disable the IGPU if I remember correctly.
First of all, start by disabling "memory context restore" and "memory power off" as indicated in this solution post. Please note these 2 settings are made under AI tweaker and under Advanced as indicated in the solution, everything is well explained ...