I dont believe there is a compatible VBIOS for the Vega 56 like there exists for the RX 480 & RX 580. Perhaps I got lucky, but the RX 580 VBIOS has resolved a lot of my issues. Thinking about it I did not have the exact same issue as what others are talking about in this thread since i always saw the Framework logo previously. I have noticed that using hibernation brings back my issues and would not complete POSTing. However, disabing hibernation in Windows fixed that issue for me.
But to answer your question, the steps involved finding a similar VBIOS on the techpowerup VBIOS database. Its best to get as similar as possible, such as with the memory vendor, memory size, and card branding. Then you would use something such as atiflash to get the new VBIOS onto the card. I had to disable VT-D in BIOS for the flashing process to work or else Windows would kernel panic. I am probably not the best source for this but I hope this is useful for further searches.