@jonah Nope, separately - I've tried the Jellyfin plugin for Kodi years ago and found it miserable to interact with 😕 Very slow, and a lot less intuitive than Jellyfin's own UI (very "everything is a list").
I plan to use the Jellyfin web interface with the "control from other instance" feature in the mobile app, so that I can essentially use the NUC as a media player target.
We've also set up an auto-hide Plasma panel for switching between applications, bound to the Menu key (so it works from my USB remote); it has shortcuts for the different media player applications and a large-UI task switcher to switch between them.
So if you press the Menu button on the remote, the panel pops over whatever is currently running (even if fullscreen) and lets you navigate between applications with the arrow/OK buttons, or if you press Menu again it disappears again.
(Jellyfin is set up to run in Firefox in kiosk mode. Altogether it *almost* feels like an off-the-shelf commercial product in terms of polish, heh)