thanks for pointing it out tho i wouldnt mine with 6600's unless i found a lorry full in a field lol. As for Linux it can be challenge but very rewaring to break free of MS tho sometimes it can make one want to smash things up in a rage if its not bad enough learning new HW then throw in an unfamaliar distribution i been on Ubuntu till now having moved to Manjaro to get these 6800s singing without windows such is the passion for that here.
6 x RX6800XT up, undervolted and playing nice under linux.

except the stale shares to sort out....
GPU1: 48C 60% 147W, GPU2: 45C 60% 155W, GPU3: 51C 60% 151W, GPU4: 50C 49% 153W, GPU5: 45C 49% 145W, GPU6: 40C 49% 148W
GPU1: cclock 1200 MHz, cvddc 868 mV, mclock 1000 MHz, Tj 54C, Tmem 66C, 403 kH/J
GPU2: cclock 1200 MHz, cvddc 868 mV, mclock 1000 MHz, Tj 53C, Tmem 74C, 391 kH/J
GPU3: cclock 1200 MHz, cvddc 862 mV, mclock 1000 MHz, Tj 57C, Tmem 70C, 401 kH/J
GPU4: cclock 1200 MHz, cvddc 868 mV, mclock 1000 MHz, Tj 58C, Tmem 64C, 387 kH/J
GPU5: cclock 1200 MHz, cvddc 862 mV, mclock 1000 MHz, Tj 53C, Tmem 62C, 408 kH/J
GPU6: cclock 1200 MHz, cvddc 868 mV, mclock 1000 MHz, Tj 48C, Tmem 56C, 400 kH/J
GPUs power: 899.0 W; total power: 1099.0 W; cost: 6.07 USD/day; 326 kH/J
Eth: New job #9a8fdd86 from eth-eu1.nanopool.org:9999; diff: 10000MH
Eth: New job #beaaa833 from eth-eu1.nanopool.org:9999; diff: 10000MH
*** 0:09 *** 10/3 22:34 **************************************
Eth: Mining ETH on eth-eu1.nanopool.org:9999 for 0:09
Eth speed: 357.727 MH/s, shares: 23/0/0, time: 0:09
GPUs: 1: 60.585 MH/s (6) 2: 59.152 MH/s (4) 3: 59.165 MH/s (4) 4: 59.154 MH/s (1) 5: 60.514 MH/s (3) 6: 59.157 MH/s (5)
Eth: Accepted shares 23 (5 stales), rejected shares 0 (0 stales)
Eth: Incorrect shares 0 (0.00%), est. stales percentage 21.48%
Eth: Maximum difficulty of found share: 772.1 GH (!)
Eth: Average speed (5 min): 355.251 MH/s
Eth: Effective speed: 425.14 MH/s; at pool: 425.14 MH/s
time for a day or two away let the hash crack on...
Have you tried changing the F-state on linux using a script? You can get a stable 62.5 MHs on average for each card.
Check out the link below, it was built for HiveOS (which is an Ubuntu variant) so it might prove useful for you: