Thanks to your work I was able to get the leds on my 6800 working when passing through only the disks to OMV. I'm now doing passthrough of both SATA controllers, so I can spin down the disks and get complete SMART info in OMV, this also works.
However now the leds stopped working, they turned red probably because ProxMox can't see the disks anymore. I've tried to apply your led guide to the OMV vm, but wasn;t able to see anything on the i2c bus, also not after passing through the i2c controllers.
Do you have any tips on how to get the leds working with the SATA controllers being passed through?