So, I got everything else figured out except how to get IPTV multicast streams to work.
The m3u entries in the playlist look like this:
#EXTINF:-1 group-title="foreign;HD" tvg-id="ZDF HD" tvg-name="ZDF HD" tvg-logo="ZDF_HD.png",ZDF HD
udp://@239.11.2.134:5000
Some channels in the playlist have http:// addresses and work perfectly fine.
I tried piping but there was no difference.
pipe:///usr/bin/ffmpeg -loglevel fatal -i udp://@239.11.2.134:5000 -vcodec copy -acodec copy -metadata service_provider=T-2 -metadata service_name=ZDF_HD -f mpegts -tune zerolatency pipe:1
All items in the playlist work without problems in VLC.