As a Plex user I'd recommend a used last-gen game console as a TV source. In my AV room upstairs I've had an XBOX ONE S for a long time and more recently I got a PS4 Pro for the spare room downstairs -- both at Gamestop. I have some games for both of them but I am more likely to game on Steam, Steam Deck or mobile.

Every Android-based media player I've had tried just plain sucks, the NVIDIA Shield wasn't too bad but at some point the controller quit charging. You can still get a game console with a built-in Blu-Ray player too and it's nice to have one box that does that as well as being an overpowered for streaming.

I have a HDHomeRun hooked up to a small antenna pointed at Syracuse which does pretty well except for ABC, sometimes I think about going up on the roof and pointing the small one at Binghamton and pointing a large one at Syracuse but I am not watching as much OTA as I used to. It's nice though being able to watch OTA TV on either TV, any computer, tablets, phones, as well as the Plex Pass paying for the metadata for a really good DVR side-by-side with all my other media.

As for TVs I go to the local reuse center and get what catches my eye, my "monitor" I am using right now is a curved Samsung 55 inch, I just brought home a plasma that was $45 because I always wanted a plasma. I went through a long phase where people just kept dropping off cheap TVs at my home, some of which I really appreciated (a Vizio that was beautifully value engineered) and some of which sucked. [1]

[1] ... like back in the 1980s everybody was afraid someone would break into your home and take your TV but for me it is the other way around