To me, this problem is still not solved. I have tried third party profiles from several suppliers. Some work, and some don't. The profiles that sync properly are of the more simple, non camera specific type (Prolost and TCP). These get automatically organized in their own folders in LR Classic and CC.
The profiles that won't sync includes camera profiles (VSCO and RNI). In LR Classic and CC they are not organized in their own folders. The color profiles are just stored in the Profiles folder, and the B&W profiles are located in the Legacy folder. In my mobile app the Legacy folder don't even exists.
I don't know if this is just a coincidence, but it seems that the sync problems are connected to the camera profiles in some way. I love these profiles very much, so I really hope it exists a solution that will work for me too!