Not sure if this is a widespread issue, or if it’s specific to Sony Bravia TVs.
But when in the Plex for Android TV app, the option to switch to 3D mode is disabled in the action menu. When using the Plex app on the Apple TV (on the same Sony Bravia TV), the 3D option still exists in the action menu. This is because the Plex app on the Apple TV, does not change the overall behavior of the Android TV, it’s just received through the HDMI and has no access to the Android system at all. So when watching Plex through the Apple TV, the 3D switching in the action menu is enabled and plays 3D movies fine. But because the Plex app on Android TV, is at the system level (thus can control the Android TV’s options), it disables the 3D option in the action menu, and doesn’t allow the user to switch to 3D mode. The Plex app for Android TV, is the only app on our Android TVs where the 3D option in the action menu is missing (tested a few of the high-end models from the past 3 years).
So please give the option for 3D switching in the action menu. I’m pretty sure it’s just enabling / switching a flag in the app somewhere.