Just updated the mavlink-router's configuration to also try on 460800, to make it also compatible with older firmware versions. It can be checked what baud rate it stayed on on the journal:
$ journalctl -u mavlink-router
...
Aug 29 18:05:25 intel-aero mavlink-routerd[795]: UART [7] speed = 921600
Aug 29 18:05:25 intel-aero mavlink-routerd[795]: Open TCP [9] 0.0.0.0:5760 *
Aug 29 18:05:26 intel-aero mavlink-routerd[795]: Baudrate 921600 responded, keeping it
Just updated the mavlink-router's configuration to also try on 460800, to make it also compatible with older firmware versions. It can be checked what baud rate it stayed on on the journal: