If anybody is interested I have created a driver in Rust for the Up2Stream Pro that connects over UART. It is more programmer friendly to use that having to directly send commands over the UART interface. It is intended for anyone who is trying to build a system using the Up2Stream Pro and wants to write the control logic in Rust using a no-std environment and the embedded-hal.
It is an early version that works for me and has only been tested on the Raspberry Pi Pico, however, as it uses the embedded-hal it may well work for other microcontrollers. If you do have any issues using it then please let me know here or by raising an issue in GitHub.