Could you maybe explain how you got this working?
I am currently trying to achieve the same. We want to have a standalone VR application for Vive Focus 3 where an external user can guide the experience by using a bluetooth keyboard directly connected to the Vive Focus 3.
I'm currently simply using the UE5.1 WaveVR Sample project and added an input button for when the "G" key is pressed. When i play-in-editor the input key from my PC's keyboard gets passed along correctly. But whenever i try to replicate this in an android build, deployed to the device, none of my keyboard inputs seem to be registered by Unreal.
Did you have to do anything special that i'm missing?