First decide what you're looking for: Some kind of Raspberri Pi style desktop replacement (or capable of that). GPU, GB's of RAM, plug in USB peripherals, fast

First decide what you're looking for: Some kind of Raspberri Pi style desktop replacement (or capable of that). GPU, GB's of RAM, plug in USB peripherals, fast external storage, ... Microcontroller: on the lower extreme of CPU power, no graphics, small flash/RAM, grab soldering iron to hook up peripherals. There's ~$0.10 parts there. Boards like the Milk-V Duo fall in between. uC like, faster cpu, larger embedded RAM, may produce video output, not suitable to run modern desktop OS. Very different beasts for very different applications.