The Mining edition of these cards don't have switchable bioses. I checked anyway, but they don't.
I tried downloading SRB Polaris V3.5, but it somehow doesn't work for me. Pimp my straps, strap editor and any other options don't work. I tried version 3.0 and that one works, but it doesn't have pimp my straps option.
After trying some other things I figured out, that the tool completely works for a different BIOS (from a RX580 8GB). Weird...
Just for curiosity, download the bid and upload them in here. Id like to see the actual file content myself and hopefully figure something out.
This is the BIOS that the cards came with.