Instead of using RTMP publishing you can ingest multiple video protocols to Castr.
If you have an HLS URL, you will be able to add it as a pull source and stream to multiple platform or using your own player.
You can change the stream mode to Pull Source and paste the URL to be ingested and if Castr can connect to the source the stream will be live in Castr.
IP Cameras can be connected using pull source and Castr supports RTSP ingest.
Hit us up if you have more questions.