The ATMega328p, the chip at the heart of all your Arduino Uno clones, ... There are also issues with any other parts nearby the micro, including the batteries.

The Arduino Uno R4 is to have a Renesas RA4M1 32-bit Arm Cortex-M4 microcontroller, and there are "no plans to discontinue the popular Uno R3" , according. About Us; ... Renesas RA4M1 super-set block ...