A lot of times I have ideas for small handheld devices I want to build which all boil down to a microcontroller/SoC, a screen, an enclosure, and a battery (could be lcd, touchscreen, or e-ink)

I just want to focus on programming the hardware so I'm wondering does anyone know if any companies make pre-made devices like this?

Something I can just buy, plug in to my PC immediately, and start programming it

Could be arduino/rpi based, just curious what exists