I have Ubuntu 20.04 and Mavproxy installed on Raspberry Pi 4. I am not able to get a connection on mavproxy to the Pixhawk cube through UART(ttyAMA0). The terminal is stuck at ‘MAV’. The wiring and baud rate are correct. If I connect via USB(ttyACM0),I am able to get a connection to pixhawk. On the wiki it says we have to enable serial port via ‘raspi-config’ for it to work. Raspi-config is not available on Ubuntu. Could this be the problem. How to enable serial port on Ubuntu ?