MakeMKV can't remove region coding on Blu-ray Discs because region coding on Blu-ray Discs isn't implemented the same way as it was on DVDs. It's essentially just a variable that's passed into the playback runtime, and if the disc looks at it and decides to use it to control the playback flow, it's ...
Doesn't work for me either, but from what I understand August is kind of a busy time for Mike. Just forwarded my dump file to him as well, so hopefully I'll be rewarded with being able to back it up soon.
You don't get the source to makemkvcon, it's in the makemkv-bin tarball, which you need. The makemkv-oss tarball contains the source for the parts that are open-source, but you have to have both or MakeMKV won't work.
Are you talking about a backed-up file tree from a Blu-ray Disc/UHD Blu-ray? If so, click the left-most button in the toolbar, select the top level directory, then the "BDMV" subdirectory, the the "index.bdmv" file, and go to town on it.
Is there even any (affordable) software that could author an UltraHD Blu-ray Disc? I know there are 100 GB BD-R XL discs, but I guess I don't know if any legit players would accept it them as "real" UHD discs...
Going into View -> Preferences, and enabling "Expert mode" (and possibly "Log debug messages") should give you more useful output. Are you backing up the entire disc, or just a certain title? John Wick 3 (as a Lionsgate title) may have been one (I haven't backed my copy up in awh...