yesterday i installed andd checked the sunnxt app in jio stb i dont think this version of sunnxt app has any dolby audio movies. because i dint see any dolby logo on recent movies which i see in android tv app. so my guess is it doesnt have dolby audio right now, but it can come in the future
no necessarily device but they might be restricting it with software.... just like they do for few android TV running pie... but again, since unlucky few received boxes with old software, it might as well be hardware but...... jio wouldnt be that stupid enough to give out inferior hardware.
As far as I know sun nxt app doesn't have any restrictions on any device to provide Dolby sound.
If a device supports Dolby it should support sun nxt app.
Jio STB has Optical Out ie SPDIF BUT no app on jio STB supports 5.1 playbacks not even Amazon prime or Hotstar the only way you can get 5.1 audio is thru the Photos app if u want to play the multi-channel movie using SPDIF port the movie has to be DTS or Dolby Digital AC3 (NOT Dolby digital plus ie E-AAC) and currently only Photos app can play multi-channel audio files or movies using Pen-Drive. no app such as hotstar or PrimeVideo has that support. trust me I have tried contacting PrimeVideo Support and jio Support all that they told me is that the H/W doesn't Support it and they cant provide any solution on this (see attached Photos of the conversation)
what we can do is to contact them again and again on this issue until they provide a solution for this