One sensor board and one control UART

[bwees]

I am building a onewheel with this firmware and want to know the steps to get a sideboard working on USART3 and regular comms on USART2. I only need gyro data from one board and would like to implement an arduino for datalogging and other items on USART2 since that is open with only one board connected. I cannot seem to find where the pins for Software Serial are broken out on the board as well (multiple other issues are opened unanswered)