Channel 107.1 is the ATSC 3.0 version of channel 7.1. Unfortunately, Plex does not yet support ATSC 3.0 channels; it is gated by the lack of support of the AC-4 audio codec used by ATSC 3.0.
There’s a long discussion of the topic in the thread below.
As far as Plex Media Server is concerned, your only option right now will be to try to improve reception of channel 7.1. That may be easier said than done given that it’s a VHF channel (RF 7).
