This guy ^^ properly knows how to flash a graphics card and how to recover from bad flashes. If you got a problem here, he's your man.
Me? The only GPU flash I've ever done is that official NVIDIA one a few years ago for the 2080 SUPER to fix something about bad port signals, can't remember what it was exactly now. Never noticed any difference and it certainly didn't brick it.
Actually, not quite true. Now I think about it, I flashed my AMD 2900 1GB* to a Pro or XT / XTX (forget which was the top model now) and that worked fine. No bricking and no instability. Performance still couldn't hold a candle to its competition, the NVIDIA 8800 GTX, but hey. I ended up getting that NVIDIA card in a firesale and it blew away its AMD competition. I still have both cards and so many other oldies in my collection.
*That was such a lot of VRAM back in 2007 and it wowed everybody! My current card has 8 times that amount and isn't considered a lot either nowadays.