Would it be possible to add support for catch-up tags in M3U? The tags typically look like this and are supported in Kodi / IPTV Simple Client:
catchup="append" catchup-source="?utc={utc}&utcend={utcend}"
Channels doesn't support catchup, as those are delivered as on demand and not as live streams. Channels only supports live streams from m3u sources, at the moment.