I cant get my s9+ to detect otg adapter, but my note 8 does without problem. I have tried different USB settings in developer mode and nothing helps. I saw ob XDA that alot of developers were having the same problem. Is there something Samsung they must know of these issues.
Have you changed the USB settings?
Plug the USB cable into the phone and the computer
Touch and drag the notification bar down.
Touch Tap for other USB options.
Touch the desired option (e.g., Transfer files).
The USB setting has been changed.