The system beep is played when the system is NOT fully up and running.
Tested on APU4 board where I hear the beep at second ~60
[ 32.038770] vyos-router: Waiting for NICs to settle down: settled in 1sec.. [ 42.015513] vyos-router: Started watchfrr. [ 42.059192] vyos-router: Mounting VyOS Config...done. [ 122.777103] vyos-config: Configuration success [ 122.872442] vyos-router: Starting VyOS router: migrate rl-system firewall configure. Welcome to VyOS - LR4.wue3 ttyS0 LR4 login: