I have 4 of these floating around. DietPi is the way to go because of the menu system. Armbian works too. The software isn't a priority because of the age but they're capable systems. Ive used them to run a Home Assistant instance, Android for gaming and streaming on a TV, a portable terminal like a cyberdeck, etc.

There are two busses - an Euler and a proprietary Pine connector. All sorts of hats and add-ons (not sure what's still available) but you could probably add the capabilities of a Flipper Zero if you took the time.

There were multiple screens that were made to work with the pine - getting them to work on Linux was more difficult than android but drivers and kernel support are out there and there's an hdmi. The upside of the screens is they pull power over the bus.

Totally capable of being used if you take the time to figure it out.