Another newbie forgot to turn on the compute mode in the driver settings. Without this mode, the RX580 8Gb video card will give a hash rate of 8-10 megahash.
https://www.amd.com/ru/support/kb/faq/dh-024Update the drivers for your video card.
FP91G is correct. Make sure to set cards to compute mode in AMD Radeon settings if using Windows. If you have questions ask here. I would be willing to help you.