For example, ‘mkvtoolnix’ (not Mkvmerge as I said previousy) it is possible to select specific audio/video/subtitle streams and render the selection to a file (MKV or MKA).
If you render just the TrueHD as in this example of my Dune blu-ray (ripped with MakeMKV) you’ll get an MKA file which will have original ATMOS (with meta data) stream and not a discrete 7.1 FLAC.
So you would need to rip your REM Blu-Ray with MakeMKV to a MKV file, load the MKV into MKVToolNix and then select/render the audio part to an MKA file. The MKA can then be ‘played’ (as music) by the Vero.
However, as I recall there were some issues with the Vero not handing MKA files properly, with respect to the ‘time’ field during playback, which I describe in this post [TESTING] Kodi v19 builds for Vero 4K / 4K + - #659 by thechrisgregory