First, thanks @Marshalleq for the post and research! As @Defq0n mentioned, udev rules don't seem to be persistent. I have two Envoy Express drives (https://www.owc.com/solutions/envoy-express) working with Unraid. Below are instructions that I followed to get it working:
Navigate to /sys/bus/thunderbolt/devices/domain0/0-0/(0-1 & 0-3 are my devices, I used cat device_name to verify within each device folder)
Display the contents of the authorized file: cat authorized
If this is currently a 0 then: echo 1 > authorized
Confirm it is now a 1: cat authorized
Run echo 1 > /sys/bus/pci/rescan
At this point, I now am able to see the drives!
Next step is to do this on boot. Used gpt4 to create a bash script: https://github.com/rossingram/Thunderbolt-Unraid/blob/main/thunderbolt_setup.sh and will report back on stability, etc. Hope this helps.