I have a Raspberry Pi 3 with a Hifiberry DAC running OSMC (nicely packaged Kodi on top of Debian) acting as my media center and recently installed Jellycon with the hopes of being able to use server side transcoding for a few formats my old TV doesn't support.
My verdict: Menu navigation is slow, but it's a native kodi integration (supports widgets) and playback works great once you made your way through the menus. You can selectively set transcoding options per file type which is exactly what I needed.
Best solution I've seen so far, as it also does IR remote passthrough over HDMI if your TV supports it. The addon works in any kodi setup of course. I think there might be a way to start playback from the Jellyfin web UI but haven't bothered with it. This would fully remedy the menu slowness, I think.