Its a limitation of the AMD Linux drivers, nothing tytanik can do about it.
I am starting to love nvidia over amd but nvidia also has some stupid limitations
I have not tired EthOS but it looks like they have something in change logs for latest update.
Major Changes:
Increased RX series hashrate by fixing hashrate drops caused by DAG growth.
Added ability to set voltage for RX series GPUs. <<< i cant validate this but since its also ubuntu maybe figure out how they did it (if it works)
yep, last ethos update able to set voltage to rx gpus