I would prefer to use the MYTVOnline 3 app instead of the HDHomeRun app but it will not recognize any channels.
I've tried using http://hdhomerunipaddress/lineup.m3u, I've tried uploading the actual file, and I've uploaded the playlist to m3u4u and tried adding it from their m3u file.
No matter what I do, it finds 0 tv channels. I get the same issue with MYTVOnline+. Every other iptv app I've used has recognized my HDHomeRun, including VLC.