I agree that RX570/580 is very good on the LBRY when dual mining with ETH, but for me its not worth it. Too much electricity, too much problems if you have 6+ GPUs and your electrical system is not scaled for this.
dual mine vs electricity usage Works much more efficient on nvidias. But thats my opinion. That is why I dont dual mine on my ATIs, only on my Nvidia.
example: RX570 - single mine ether, 125Watts, dual mine ether+lbry goes to 180-185watts.
Nvidia 1060 stuck at 85-90 watts (with lower TDP but still efficient mining hashrate). dual mine eth+lbry.
According to WTM, I lose about 4% of my ETH profit if I dual mine because of the electricity difference but I get about 15% more from LBRY, so 11% more profit in dual mining. I live in Canada and electricity is cheap that's why. I think I have enough power in my circuit for only 4 cards but I might have other issues like wiring and stuff. Because logically 4 cards should not make lights flash