The technology is still new enough that getting the cheapest 4K screen you can find is still a really bad deal.
For my computer, I use a 32" LG 4K monitor, and it's great. No 'smart' features found there.
But I can't find a 4K monitor in the 42-50" range that has multiple HDMI inputs that is not incredibly pricey (e.g. broadcast/commercial realm) I could use in my living room.
It has 4 HDMI inputs and a USB-C with display port. It even has a remote.
It's an IPS panel though. From what I hear not everyone loves those.
Amazon has it in France for around €600.
[0]https://www.lg.com/us/monitors/lg-43UD79-B-4k-uhd-led-monito...
My receiver is older and doesn’t have HDMI in, but this solution works well with the TV I have. When a device is turned on, the TV wakes up and switches to that input. If the PS4 is on and I turn on the Apple TV, it will auto-switch. I never need to touch the TV remote at all since the devices go to sleep automatically, which is nice. Apple TV remote handles the receiver volume, and the audio input never changes on the receiver, so I don’t need the TV or receiver remotes at all.
I'm wary of using HDMI AVRs today because they add input lag.
To all the folks reading at home... I would remind everyone that a TV is not a monitor.
I got a relatively inexpensive LG 43in TV to use as a desktop monitor. I've had issues. Beyond the usual "make sure your graphics card actually supports 4K" and such, you also need to take some time to dig through the TV settings when you are using it on a PC.
In particular, you definitely want to turn on "game mode" or whatever it will be called. This turns off the internal image processing that can add hundreds of milliseconds of lag to the display output. You'll also need to find the settings to turn off the overscan. Many TVs will, by default, zoom into the center of the image, cutting off the edges a little.
I've mostly gotten over the other issues with using a TV as a monitor (color settings and such), but if you want to save yourself some hassle, just get an actual monitor.