You ought to be able to get the YouTube above working on Android - I’ve got it working here and it seems OK.
Xibo supports RTSP over local video Widget (depending on codec), HLS using the HLS widget or indeed Embedding YouTube via the link above. The codec support is very much dependent on the device - I can’t recall whether the J18 can do that, but if you have any doubts I am sure the guys over at DSDevices would be happy to help you with that.
These are the codecs supported by Android more generally: https://developer.android.com/guide/topics/media/media-formats