I had a faulty Sapphire Nitro+ RX580 8GB that I got from a scammer, turned out it was a mining unit.

I found this guy by chance to see if he can fix the broken GPU.
Apparently he can but it is not worth it to repair money-wise but he can repair it. His diagnosis was fast. I thought it would take around 30mins for a diagnosis, he did it in under 15 minutes or less(I don't remember how long it took but it is very fast).

His service is good. Highly recommend.
Will probably go to him again if my current GPU, an old R9 270 breaks.