"I am using Dispatcharr as an M3U and EPG source in Channels DVR. Channel logos show correctly in the web guide but do not appear in the Channels app on Apple TV or iPhone. The same source shows logos correctly on Android. The logo URLs in the M3U from Dispatcharr point to the Dispatcharr server's cache endpoint. Has anyone else experienced this with Dispatcharr as a source, and is there a fix?"
Just out of interest are you serving the M3U over https or just http?
I seem to remember something about them needing to be https, but it's been a long week...
I use Dispatcharr but don't point to the imagecache repository but to the original link it's capturing and re-showing.
...../output/m3u?cachedlogos=false
Not sure that's what is causing your issue but perhaps something to test out to see if non-custom logos show in the clients this way?
Thanks for all the help. The fix was adding ?cachedlogos=false to the M3U URL in Channels DVR. This causes Dispatcharr to pass through the original logo URLs from the provider instead of its own cache endpoint. Logos now show correctly on Apple TV and iPhone.