I tested the file which wouldn’t play on iOS and iPadOS on the Plex TV app on the Sony X900H. The file actually manages to load but it buffers a lot. It took almost 30 seconds for it to start playing and then it freezes (without loading bar) and resumes, etc. The bitrate is relatively low (18Mbps) compared to other Blu-ray remuxes (30Mbps+) I have which play fine in the same setup. While the file was playing, I confirmed it was Direct Play for both video and audio on the server.
In my case, the file plays perfectly on ATV, macos and windows plex client in direct play, the problem is just ios and ipadOS. This is not an issue with the file, and it can play ion the iphone and ipad just fine with infuse, emby, etc… So this is very clear where the bug is.
@Craig_Holliday let me know if you need a proper Dovi 5 file to test, have plenty here, that I can share using gofile