Hi

i will tell how i am managing such cases.
Find another card just like the damaged one with same memory type.
Put those 2 cards on the board and start windows, it probably will show 1 gpu and 1 with problems or just 1 but the other will be still detectable from atiflash tool.
Use ATIwin flash(ATIFLASH) to download the BIOS from the healthy card.
Use Polaris bios editor to OC the bios and save the new bios.
Flash the non working card with atiflash .
atiflash -p 1 biosModed.rom
I never used moded bios from techpowerup they just don't work, but at least here are all option of atiflash exe
https://www.techpowerup.com/forums/threads/how-to-use-atiflash.57750/

Cheers