Think you're confusing two things.
The first is how you get an m3u playlist from Channels DVR.
http://192.168.50.215/devices/ANY/channels.m3u
This provides an m3u playlist and takes parameters like format=ts (for an MPEG-TS playlist), or nothing (for an HLS playlist), or codec=copy (for an HLS playlist)
The second is the url inside the returned playlist that gets passed back to Channels DVR when that item in the playlist is selected to play/record.
Inside an HLS playlist would be
http://192.168.50.215:8089/devices/ANY/channels/2.1/hls/master.m3u8
Notice the /hls/master.m3u8
that specifies an HLS stream
Inside an MPEG-TS playlist would be
http://192.168.50.215:8089/devices/ANY/channels/2.1/stream.mpg
Notice the stream.mpg
that specifies an MPEG-TS stream