What kinds of privacy settings does the browser allow? What kinds do the maps/GPS allow? Are there privacy settings showing but not working? Are there settings not present where there would usually be?
Take a picture, save it. Edit it. Can you undo the edit? Is the original able to be saved apart from the edit?
What kinds of accessibility features are available? Contrast, font sizes, haptic feedback, etc.? What's missing? Can you figure out where you are on the device, if you started from the home screen, without looking or while squinting and the device is an arm's length away?
Given the techie/open source bent, and even though there is no file manager app by default: how does the system handle ZIP/RAR/TAR files which come from downloads or being sent (Bluetooth, email, etc)? Can you view/extract the archive? Are you able to navigate to what you unpacked after its uncompressed? Are there processes which run/hang when you try to uncompress or view these kinds of compressed files?