Currently, visible feedback on hardware chassis running VyOS is limited to hardware controlled LED status change and very few triggers:
vyos@apu2c4:~$ cat /sys/class/leds/apu2:green:led3/trigger none disk-activity disk-read disk-write ide-disk cpu cpu0 cpu1 cpu2 cpu3 panic mmc0 phy1rx phy1tx phy1assoc phy1radio phy0rx phy0tx phy0assoc phy0radio
None of these may signal traffic on "virtual" NICs like bridges, TUN/TAP devices and similar. However, it may be highly desirable to just "see" if a tunnel is up / has traffic on it or not.
This feature request enables the Kernel LED trigger modules that are curently available.