VLC doesn't notify android of serving opus files

I'm not yet sure what the true reason is, this is the behaviour:

when I click an audio file of type *.opus in a filesystem tools like x-plore (or others), then there is no suggestion to use vlc. That is, why I think, that vlc didn't register for this service. On the other hand, if I start the VLC app and open the file inside vlc, then the audio file will be played like a charm :-).

Env:

Samsung Galaxy S6

Android: V7.0, Kernel 3.10.61-13115714

VLC: 3.0.11, 700b2910c0