USB connection Fenix 6X to Android device

Hello, I tried to connect my Fenix 6X Sapphire to my phones (Samsung S21 Ultra & Samsung S10+) using an OTG cable (this cable works perfectly with USB keys)

When doing so, I can't access the watch.

As I travel a lot (without a laptop) and need to upload maps/ gpx frequently to the watch, I was wondering if you guys had any solution ?

Thanks