I have a solution here, but this demands patience.
The problem is from Microsoft and basically from the BLE patch they introduced by fixing the CVE-2019-2102 vulnerability in 1903. The same vulnerability used to impact PSMoveService as well, but reportedly was patched by the developer somehow. Against all odds, I did not manage to also pair 2 PS3 Move controllers to a 2004 Windows 10 (although reportedly fixed).
Coming back to the GearVR controllers, the message you will get in the System Event log would be: “The device (device MAC) is trying to distribute an Identity Resolving Key that is already used by a paired device. The pairing was rejected, if the intent was to pair with this device, you may need to first delete the existing pairing information.” Perhaps Greg cannot solve it unless writing a BLE stack patch or to deactivate .
Basically, what I have done to have 2 Gear VR controllers in Win10 2004 is install 1809, pair all devices, then upgrade to 2004. I know, it sucks, but it works. Of course, when accidentally one of them is unpaired, I will have to reinstall everything. Once again, this happens only during pairing. It was a dick move by MS, but it is as it is.
Same applies to almost any BLE device pair like cheap VRBoxes. What I will be experimenting these days is for example GearVR + Daydream controller. But I think safest is to just go to PS Move controllers, if they are the same price.
IMHO the 6DOF hand tracking of GearVR + Kinect360 is horrible, especially when you have games where wrist moves are important (swords or boxing like Creed). I think PS Move controllers are better.