My Plex client on my Fire 4K Stick is v8.8.1.21332 (0798457a). I am not sure that I have ever seen consistent playback on live TV. That’s surprising because everything else besides live TV plays perfectly. Live TV used to buffer and lock up constantly. Now it locks up less frequently, but always exits back to the guide within 5 minutes. As mentioned earlier, my Roku client and my Samsung Smart TV clients never have an issue with live TV.
I prefer the Firestick 4k as a client to the Roku because I am deeply vested in Amazon automation. Also, I much prefer anything that does Android TV as opposed to Roku or proprietary Smart TV because I have the option of running any Android image.
I had considered getting an Nvidia Shield, but both the price and lack of significant built in storage has dissuaded me. My Fire TV 4k is a constant source of annoyance with the lack of storage. The 8GB device uses a solid 3GB for the OS and with a small collection of apps I generally have maybe 850MB free. I’ve had external storage configured on it, but lately changes to FireOS have caused that storage to be disconnected.
I have considered the new Chromecast with TV, but again, the same storage issue. Why don’t these folks put 16GB in instead of a stingy 8GB? Have they ever used one of these devices? I often wonder if the Plex Live TV on the Fire Stick 4k is resource constrained somehow.