[jacanuck]

I could be wrong but Dolby TrueHD and DTS-HD passthrough works in my environment (kodi 18 and spmc 17.6). And if I recall correctly I also tested passthrough for these codecs with test files.

Also page 1 says that it should work.

I believe DTS HD and True HD (and atmos) don’t work in mibox S. Just mibox 3. 

 I opened a support case with Xiamoi via support chat today - no indication of timeline, but the chat rep at least promised to escalate for me (whatever that means).  I'm not sure I'll receive updates, no case number was provided (but he said I could chat in the future and provide my telephone number for reference / updates).