I am running 20x 6600XTs across 3 rigs all on HiveOS. I use TRM for the miner. I have run into the same issue when starting up a new rig, or modifying an existing rig in any way, for example, adding a new 6600 XT GPU.
Here is my current solution. This applies only to the 6600 XTs I have been working with. Before starting up a new rig or making any change, remove ALL OC/UV settings for the 6600 XTs, in other words reset to the AMD defaults. Bring up the 6600 XT GPUs on the defaults and let the system stabilize for a few minutes. The rig should come up this way without the “No Temps” or “Drivers installed with errors” problems. Don’t wait more than a few minutes because you don’t want you GPUs to overheat. Next, while the rig is still up and running, go into HiveOS → Farm → Worker → GPU settings dial and set you OC/UV values. The OC/UV settings will take while the rig is up and running and you should be good to go.
Also note, if your settings are too aggressive, then when your rig has a reboot you will run into one of the same two errors listed above. If so you may need to back off on the OC settings, or just know that you will need to go through the same sequence if there is ever a reboot. However, the “No Temps” error is a HARD Error – the rig will not come back to life without a power off / power on reset. So I set the rig BIOS to restart at Power On, and run the rig on a smart PDU so I can power off / on remotely.
Hope some of this helps.