I have had a look at the guide here
https://tvheadend.org/d/3934-export-all-channels-of-tvheadend-inside-a-m3u-playlist-file
I have tried all the options as a M3U URL mentioned in the comments but not a single one works with Jellyfin.
I am not sure what else is to try. I know there is a plugin in Jellyfin but I prefer to use M3U and XMLTV URLs instead.
Also can good answer for this be put in the Docs for future reference.