Hi there,
TLDR; I'm working on a macOS app for enabling an all-Mac workflow for converting 3D MKV to FSBS:
https://medlund.com/makesbs3d-howto/
I've been keeping an Intel NUC around to use MakeMKV + BD3D2MK3D to convert 3D movies to Full Side-by-Side for viewing in Meta Quest VR headsets.
A year or so ago, I managed to put together an app on Mac for my own use to fill the BD3D2MK3D gap and do it entirely on my Mac. I had an issue sharing it with others though because of Apple's requirement for signing embedded helper binaries with a hardened runtime that I just couldn't figure out.
Well, after setting it aside for some months and then having a fresh look at it, I had some success. I now have MakeSBS3D in beta testing using TestFlight. Check out the post for more information.
~M