The unfortunate reality of Jellyfish is unless it ever comes baked in to Xboxes and smart TVs it doesn't solve the problem all media centers that aren't Plex have. If you can't add it from an app store and use the tv remote or game controller to navigate it no one I know will use it. So its Plex and nothing else until dethroned because I'm sure like most I'm running an internet facing media server for others.
Which is probably why they've invested so much time into getting their official clients for Android TV, Roku, LG's WebOS, iOS, Android, and more out there for people to download, and have clients for several additional platforms in various stages of development or app-store approval.
I’ll second this, not to mention the first class support Plex has for audio content. I have dedicated apps for my music and my audiobooks. I haven’t found anything close to that in the Emby or Jellyfin world.
I downloaded it on both my Roku and Fire ( Amazon ) devices just as easily as any other app.
Of course, the applications use the native remotes for these platforms. Since I am the one that puts all the content on Jellyfin, my less technical wife sees it like any other channel ( like Netflix, Disney, or Prime ).
I do not use AppleTV anymore but I installed it on my iPhone as well. I had used Plex before. I did not a find Jellyfin any harder.
I use an Nvidia shield and it has a Jellyfin app (along with basically anything else on Android, which is why it's been perfect for me). User friendly while still being flexible enough for most anything I want to throw at it.