Jeez man, two PMs, and the same post in two threads? I've posted here every day for weeks, you don't need to scream to get a reply
Anyway, obviously the EFI I posted works fine for me. However you have an X5700. So try adding boot arg agdpmod=pikera
Also, I uploaded a more recent EFI than that - there's one dated 23rd November, in this thread. It's 99% identical, but the 23/11/20 EFI is the one I used to update to Big Sur, so I'd use that one to be safe. I've re-attached it here.
This EFI has AirportItlwm disabled, as the kext included is still for Catalina. That will need to be updated to the BigSur version if you plan to enable AirportItlwm. But I don't recommend enabling it for install/update, only once the Big Sur install is known to be working fine.