It looks like Radeon Software 21.6.1 is not compatible with PhoenixMiner 5.6d with the Radeon 6800. I've gotten reports that the 5700XT is fine with the new driver, but my 6800 keeps causing a fatal error when trying to start mining. Single GPU in the system, so nothing else to cause conflicts.
I wonder if this is the driver which allows us to do Fast Timing on Linux for the RX 6800. And if this can also do core voltages under 700 mV then I can finally move all my 6800s to HiveOS.