The phone I use has constant battery charging protection. I checked before using it for that. But yeah, definitely check for that before using it that way, or remove the battery (if the phone will still run without it).

I use one as a camera monitor for my kids’ baby monitors.

A more general idea would be setting up a weather/forecast display.

Played an old LoTR game for the SNES that was so full of bugs, it actually held my interest longer than it should have because I was curious whether the game could even be completed.