Here is the GPU
Gigabyte RX 570 Gaming 4G (Hynix mem)
Stuck with low hashrate at 18Mh max. Nothing helped. Then the reason was found. Default stock bios had very low Power Limit, only 90w, so the card could not run at required clocks.
Changing Power Limit to 128 totally solved the issue.
To my understanding in Windows AfterBurner can raise that power limit from interface, but in Linux please check your cards when you flash timings. If you later set manual OC clocks to core and mem then you don't need PL to be low, you will limit it by your clocks and power states.
Problem 18mh, stock bios (
Solved 29.5mh + pasc280