Hi @dev3,
As stated in our documentation of sourceConfig.add(subtitleTrack:) we do not support side-loaded subtitles in combination with the system UI, which is the default on tvOS.
You will need to build a custom native UI in order to get support for side-loaded subtitles on tvOS.
If you think this should be part of our SDK, please open a feature request.
I see that you are still using the term SourceItem in your code snipped which was replaced by the SourceConfig in v3. If you are still on a v2 version of the iOS Player SDK, please update to v3 as v2 is already deprecated.