Yes, it's possible to multistream HLS in Castr.
You can multistream HLS as well as creating a livestream which is pulled from an HLS URL.
In Castr dashboard:
- Create a new Livestream or Simulcast (Multistream)
- Change Stream mode to Pull Mode
- Paste the HLS URL and click on Save
You will be able to multistream HLS to multiple social platforms as well as using your own player using Castr Live Streaming player embed.