Does OSMC skin show Dolby Atmos flag on movie library already at update 2018.12-1?
It does if the filename has atmos in it, i.e. mymoviefile.atmos.bluray.mkv
Not sure if the filename doesn’t, as I’ve never tested that.
This is the long answer:
It relies on whether Atmos, DTS:X or AURO-3D are present in the file name as described in the link AND whether the primary audio track is one which can be the base for Atmos, DTS:X or AURO-3D: e.g. an Atmos label does only show up, if Atmos is present in the file name AND if the primary audio track is Dolby TrueHD or Dolby Digital+.