Hi everyone,
Just a quick update for those of you who are still trying to install ChromeOS/PrimeOS. After a lot of trial and error, I was able to successfully install PrimeOS on Unraid 6.8.3.
I used the ChromeOS template, using Machine type Q35-4.2, OVMF Bios and SATA for all storage. Also, the only version I was able to install was PrimeOS Classic v0.4.5. NOTE: I wasn't able to get the the Mainline and Standard ISOs to work, only the Classic version.
Also, to install PrimeOS, I had to use the Advanced->AutoUpdate option in Grub once the VM boots from the ISO.
Once you install PrimeOS, in order to get PrimeOS to use Ethernet instead of Wifi, go to Settings->PrimeOS Settings and enable "Show connection type WiFi to apps"
Enjoy!