Hi,
I am trying to run MAVROS on a companion computer. MAVROS will only connect when the baud rate is set to 57600 B/s, I want to run it at 912600 B/s (I am connected via a USB to TTL adapter to TELEM_1)
It seems like an issue with your adaptor, as many people use baud rates higher than 57600 with their Cubes. Try 115200 as a test since most devices should be able to handle that.