Both the Arduino Nano and Uno can be powered via their integrated USB connectors. This automatically supplies regulated 5V power to the board, allowing you to use any USB-supported power source ...

The Arduino Uno-compatible board has an MCS-51 (often called 8051 instead) instead of the usual ATmega328P/ATmega168. Specifically, [ElectroBoy] uses the AT89S52 .

The Arduino UNO R4 Minima and the Arduino UNO R4 WiFi. ... the UNO R4 WiFi introduces a built-in 12×8 LED matrix, a Qwiic connector, and a VRTC and OFF pin. ...

Like the Nano, the Micro's size and male pin headers make it perfect for prototyping with a breadboard. However, Arduino also offers this board without headers pre-soldered.