Thank you, everyone. The bottom line is most discs presently use a single, large m2ts for each of the main features, and MKVToolsNix can be used to create a lossless MKV when seamless branching is the case. However, there is no freeware m2ts muxing or combining that is compatible yet with UHD Blu-ray, but it should be coming soon from what I gather online.
EDIT: What I wrote above in italics is false. Copying the single main m2ts from a UHD Blu-ray disc works, but this is ever so slightly broken. Playable is flawless, but audio tracks will not show their language. You need to mux the m2ts to fix this. This brings me to my next point: what I read online about tsMuxeR muxes causing jumpy and out of sync playback is a bunch of bunk. Either the person who claimed this was not using it properly or is using a broken media player. Simply use BDinfo 0.5.10 to determine the correct mpls Blu-ray playlist file. Then select this mpls from the Blu-ray image in tsMuxeR just as you would with a normal Blu-ray. Select all the audio, video, and subtitle streams. Finally, mux it all together into a m2ts file. All my UHD m2ts muxes work perfectly in both MPC-HC and Kodi 17. In addition, the muxes will show the language for each audio stream which the unmuxed single, large m2ts from the disc would not properly show.