M5Stamp C3U is an update of the M5Stamp C3 RISC-V IoT module with heat-resistant cover, support for WiFi 4 and Bluetooth 5.0, that does without CH9102 USB to TTL chip, relying instead on the internal USB interface of ESP32-C3 processor to handle serial programming of the firmware, and gaining on extra GPIO pin in the process.
While several ESP32 processors come with a built-in USB interface, many boards still use an external USB to TTL chip such as CH340 or CP2102 to handle the serial interface used for debugging and flashing the firmware likely because of limitations when using ESP32-C3’s USB serial/JTAG controller console, but M5Stack probably considered those to be workable, and the small cost-saving beneficial.