@jcaron Yes, you could make a simple passthrough script between UART0 and UART2 I think. That may however conflict with the normal LTA firmware, and you migth have to use WiPy firmware for the device, which ignores everything besides the ESP32. I do not know wheter is is fast enough, and you have to deal with the complete modem configuration.
The physical UART pins to the modem seem accessible on FiPy only. On GPY, TX and RTS are connected internally.