You’d probably get something like [ElectroBoy]’s 8051-based Arduino Uno. The board itself also has some differences from the original Arduino Uno. First of all, it has a USB type-C port ...

This feature isn’t exclusive to the Leonoardo, as [Michael] explains in a build he sent in – the lowly Arduino Uno can also serve ... to have your old Arduino board gain some of the features ...

Connector to add external battery to real-time clock (RTC) inside Renesas MCU (MCU RTC power pad held to 5V rail on Minima) Secondary (wireless) processor: 240MHz 3.3V dual core 32bit Espressif ...