I did it (What OP asked for)
I flashed the 50th Edition bios into my 5700 non XT.
Note that I have the reference design from MSI and that one share the same bios with many other 5700 reference.
Be sure to check that the BIOS you flash over have the same memory support... Just to be sure.
Also I do not have Windows.
And that manipulation of flashing a 5700 50TH BIOS in a 5700 cause my Linux kernel to dump a ton of IOMMU error and the card did fail to initialize.
But disabling the IOMMU in the BIOS made it work just fine. My 5700 non XT stay at 1980 Mhz almost all the time when i'm gaming, thanks to my overly abusive cooling setup.