I don't find HDR all it's said to be cracked up to be. 9 times out of 10 I turn it off and the flat blown out picture comes to life. But then some movies and shows HDR is the only way to watch them.
Range matching is your friend.
processed HDR is bad, when the aTV "upscales" SDR into HDR.
If you have the aTV in HDR mode, but not range match mode, then any SDR content is processed by the aTV and turned into HDR, with normally less than desirable results. Blown out is how I would describe it.
put the aTV into 4K SDR mode, and turn on range and frame rate matching, then SDR content is played SDR, and when you play HDR content the aTV will change to HDR mode.
You could put the aTV in HDR mode, with range matching, and achieve the same affect. (it will switch its output to SDR when you play something that is SDR)
The main reason I keep mine in SDR, is every time you change the video signal type, the TV will black out for a second or 2, At least for me it's a longer blackout when changing range, and since most of my stuff is SDR, I encounter that blackout less if I have the aTV default to SDR.
Plus it helps to make sure HDR actually kicks in, since my TV has a small popup when it changes to HDR or Dolby vision.