Is there any way to watch Showtime shows on Samsung Gear VR?
One idea is to use a Plex account to play the video from the web interface you can access from Oculus Browser or Samsung Internet (it also seems to be supported by PhoneCast).
Then can try to use this client whose Github page claims to be working with TV shows.
I have not tried it (neither Showtime), so I cannot guarantee anything, but you might want to try this solution.