@arh4e This forum is supported by members that freely give their time to help others - please keep that in mind moving forwards.
As your motherboard has the latest BIOS with a capsule you will need to use the correct version of FPT to downgrade as EFIflash cannot downgrade from this BIOS.
The Z490 platform uses Intel Management Engine v14.0 and v14.1 so you will need the corresponding FPT version to downgrade your BIOS.
BIOS F21 has ME Firmware v14.1.53.16.17.
If you go to this thread → Intel (Converged Security) Management Engine: Drivers, Firmware and Tools (2-15) you can download the ME System Tools for your motherboard (CSME System Tools v14.0.20+ r20.rar) from this Mega link.
The package ‘CSME System Tools v14.0.20+ r20.rar’ contains the 64-bit Windows version of FPT (FPTW64.exe) v14.1.60.1790 (and the EFI version if you’d prefer to use that).
As your motherboard has no Intel Ethernet Adapters you don’t need to worry about erasing the MAC address, however there is always a risk when flashing any motherboard BIOS (especially from within Windows) so I will give the usual disclaimer:
DISCLAIMER There is always a risk when flashing the firmware of any motherboard. You must decide if you think the risk is worth it - if you don’t know how to recover your motherboard from a bad flash then I don’t recommend that you attempt a BIOS downgrade. I am not responsible for any problems that arise from your actions. While I have performed a downgrade on two Gigabyte Z390 motherboards (Z390 UD and Z390 AORUS PRO WIFI) I cannot 100% guarantee that you will not run into problems.