I am having the same issue. Apple TV 4K on a TCL tv. Any time I push mute on the TCL remote, or lower the sound to zero on either remote, it blacks out the screen and I can’t get it back without unplugging the Apple TV and turning the TV on and off. It’s maddening.
This isn’t an issue with the Apple TV remote since it happens with the TV’s normal remote as well (note: it only happens when using the Apple TV, when in the normal installed TV apps it does not occur). This is an issue with the Apple TV triggering some kind of black out command when volume hits zero on the TV.