Have been experimenting. Trying to get the FAST IPTV channels into Tvheadend so as to play without locking up when they hit a commercial.
Have had some success and thought I should mention it.
I set all m3u sources to stream_type m3u8redirect
and turn off any other filter (which I would guess do not make any difference in the case of m3u8redirect).
then downloading the playlist for just the m3u section:
wget http://idaddress:6077/M3U/channel.m3u
and process it with this sed command:
sed -i "s|^http|pipe:///usr/bin/env streamlink --stdout --default-stream 2100k,2142k,576p,540p,504p,720p,480p,432p,404p,360p,288p,216p,best --url http|" channels.m3u
then using the resulting file as input for IPTV Automatic Network on Tvheadend.
Some channels work better than others but most work better than any other way I have tried.