I'm a long-time Plex user and up until a couple months ago I had been using mostly Roku clients. I decided to switch to Apple TV's because of the Apple ecosystem features (airplay, photos, apple music, airpods, apple watch/iphone as remote, etc, etc). The only thing I miss about Roku is the Plex app (and the interface). I've been disappointed with the Plex Apple TV app for some time, it falls short in a lot of ways.
I'd been putting up with it for a few months now, and none of the alternatives really did it for me (MrMC/Infuse), but I've found a solution that works for me.
I decided to try sideloading Kodi and downloading the official Plex addon for Kodi - boy it was a world of difference, it solves nearly all of the issues I and many others on this forum have with the native app.
- YOU CAN PLAY 4K/HEVC MOVIES IN ANY CONTAINER WITHOUT TRANSCODING (there isn't even any remuxing, it's all direct play)
- The old interface is (mostly) back.
- No more reloading the library on the home screen constantly (and waiting every time you go back to the home screen) - the Kodi addon actually seems to open up a streaming connection to the Plex server for library updates (I believe?).
- Playlists work properly, and I can view what's coming up in a playlist via the OSD (This is a huge feature for me as I like to shuffle a playlist of random reruns when I watch TV and skipping through until I find an episode I haven't seen recently takes ages). In the same vein, the OSD in Kodi will also briefly show what is about to play, unlike Apple TV where I have to drag down from the top once it starts playing.
- There are onscreen controls and more scrubbing options.
- Real, actual FILTERING and SORTING options.
- No longer does pressing back repeatedly take you to the tvOS home screen for no reason.
- The skip buttons on the IR remote (and Siri skip) work again.
- DTS passthrough works (with some effort).
- Forced subtitles and subtitles for non-native audio work automatically again.
- There's a 'repeat' toggle.
- You can delete movies/episodes/etc from the UI.
- No more whatever this search UI bug is - https://i.imgur.com/lPbN3tu.jpg
- No more obnoxious left side menu, and you don't have to drill back through 20 different pages to get back home - the workflow for the Kodi addon makes a lot more sense.
- It has Photo slideshows (literally the post right above this one).
- Videos start much faster and seek instantly, no more staring at the dumb loading icon.
- As a bonus, both Kodi and the Plex addon for Kodi are open source - so if there's something I don't like about either one I'm able to change or fix it on my own.
There are some cons (for me, perhaps others have different use cases):
- The biggest con is that obviously Kodi isn't available on the App Store and sideloading it for more than 7 days at a time requires a paid developer account, HOWEVER @davilla - the developer of MrMC - said that they intend to get the official Plex addon working on MrMC at some point.
- The frame rate of the interface is a bit low for some reason (seems like 20fps or so), and thus is a bit less smooth - may not be an issue on ATV 4K - I don't think this happens on MrMC.
- Channels and News (oh no, the horror) aren't available. Kodi itself has hundreds more addons than Plex does Channels, but you have to leave the Plex interface to access them.
- You cannot 'fling' from the iOS/Android apps or Plex/Web (though that required a convoluted relay server anyway). As a result there is also no Alexa support yet (planned feature).
- You lose rotten tomatoes reviews (but not ratings).
- When typing something, the native Apple TV onscreen keyboard doesn't work for some reason - it allows you to type in the box but whatever you type isn't passed along to Kodi. You have to use the keyboard in Kodi (by extension, typing on your iPhone does not work).
- I found the 'known issues' thread that lists the rest of the limitations https://forums.plex.tv/discussion/246916/planned-features-and-known-issues
Personally, the benefits outweigh the drawbacks to the point that I'm going to just pay the $99/year for an Apple developer account until MrMC supports the addon. There are a handful of other very good apps that they won't allow on the App Store (emulators, for instance) that make the price bearable.