In my honest opinion it's not worth trying to get Jellyfin working if you plan to use an Apple TV as the client. The only client that is halfway decent for Apple TV is Swiftfin and it's nowhere near as polished as Plex. The watched/unwatched indicators also don't work currently (at least for me), which is a dealbreaker imo.
I'm running Plex and Jellyfin side by side. The only thing I'd use Jellyfin for is remote streaming. It's a shame, because I really want to switch to Jellyfin, but it's just not working for me because Apple TV support is so bad.
You should take that chart with a grain of salt. It takes a while for Garmin to get to know you and for the stamina estimates to get more accurate. When I switched to Garmin it would say I was at 0% stamina one hour into a four hour ride, which is obviously wrong.