A program compiled with RUI throw an error (1) if UART2 is initialized when running. However if UART3 is initialized returns OK (0).
Unfortunately RAK811 breakout board does’t have connections between UART3 (PB10,PB11)
It seems that UART2 have connections routed to header pins(PA2,PB3).
It is possible to add compatibility in RUI for UART2 ??