I have been following this thread for a while and may have some insight. I have a 2020 Bighorn ORP, and have the intermittent clunk problem myself.
After replacing the rear sliding window assembly and recently having a break moan kit installed I was not looking forward to another trip to the dealership.
At about 34,000 Kms I started to notice the dreaded "clunk" mostly appearing on my way to work as I always drive the same route and encounter a washboard of bumps coming up to and leaving a stop sign. The same clunk showed up each time but seemed to be worse in cold weather ( -10 to -30 C, not sure the exact conversion to F). After reading about the sway bar and some issues with body mounts I took it in to my local dealership. They were unable to re-create the sound but went ahead and torqued the sway bar for me anyhow, not finding it to be loose.
So i went on my way and over the next couple days nothing seemed to change., the clunk always returned. Not deterred I decided to video tape the sound with my phone for a couple days, while driving 10-15 km/hr over the bumpy gravel road. This resulted in some pretty good evidence for the service tech and he was quite concerned once he heard the sound himself. So again they took my truck for a road test and after a lot of road testing they were able to replicate the sound!
Upon inspecting the front end again, they found that the coil spring (not the strut) was the culprit. What had happened according to the tech was part of the protective coating on the spring (for rust protection i assume) had peeled off and jammed itself up high in the spring housing (sorry if i am not using the correct terms exactly). They have the part on order and is getting installed tomorrow. Hopefully this will remedy the problem for myself, I will update this thread once I do some road testing tomorrow. Hope this may help some of you.