Using MI Fallout (DV + Atmos), I looked at the following:
1) Demuxing with EAC3TO - although it listed the EL as track 3, when all was demuxed, the EL layer was left behind. I could manually demux this layer later.
2) Demuxing with TSMuxer:
a) Using the Stream to demux, both the BL and EL were checked off to be demuxed.
b) Using the Playlist to demux (same length), only the BL was checked off to be demuxed.
3) Demuxing with FFMpeg - using the method in this thread, the EL and BL HEVC files were identical to the h265 files created by EAC3TO.
4) The Dolby VES muxing operation described in this thread worked flawlessly on both the BL/EL HEVC and the EAC3TO h265 files.
5) The final MP4 muxing operation (GPAC 0.80) was unsuccessful
![Image](GPAC-Issue.png)