Installing rocm 4.5 directly with 5.11 kernel will result the system recognizing the gpu, however I cannot set the fan speed.
You can try to add the fan speed directly from the miner and not from the Radeon software,for example Phoenixminer supports it with -tt option,you can set the minimum fan there.I would try this but the problem is I don't have a RX 6700 XT to try out.
I had the same problem with RX 570 with AMD drivers and I downloaded a script to set the fan speeds,it worked back then,the link is below but keep in mind that I used it in 2019 and I don't know if it works anymore for the newer generation of cards,however I would try it as a last resort.
https://github.com/DominiLux/amdgpu-pro-fans/blob/master/amdgpu-pro-fans.sh