Why are subtitles not shown when casting from Android/iOS to a custom receiver app?

Android & iOS v2.x.x SDKs use Player API Level v7, thus requiring the Web SDK v7 on the cast receiver. This is automatically correctly configured in case Bitmovin's default receiver app is used.

For custom receiver apps to properly work with the Android & iOS v2 SDKs the cast receiver v7 sample needs to be used instead of the cast receiver v8 sample.

More details about how to create a custom receiver application based on the v2 of the Chromecast Receiver SDK, can be found here.