OTG cable: Samsung and Garmin Tourning
For touring I plan routes on an Android phone then transfer them as a .gpx file to my Garmin and use the Garmin to follow the route as well as record the actual track. My Garmin uses .gpx directly, some do not.
All the OTG connection has to do is let me move files between the Android phone and the Garmin. I can also move track files created by the Garmin to the Android. The phone end of the link is used to control these transfers. The phone plays the part of a laptop or other PC.
It sounds like you are able to do file transfers and I'm not sure what other result you were expecting.