You can specify for Preseem to monitor a vlan by opening up the config file in

vi /etc/preseem/config.yaml

The parts in bold are what get added.

bridges:
   br0:
     addressSpace: default
     802.1q:
       inspectDefault: false
       vlans:
         2:
           addressSpace: default
           inspect: true
         10:
           addressSpace: default
           inspect: true

In the above vlan 2 and 10 get added and should now be inspected.

Save the file and restart the services

systemctl restart preseem-netdev-manager.service 
systemctl restart preseem-node-manager.service 
systemctl restart preseem-health-manager.service 
systemctl restart preseem-telegraf.service 
systemctl restart preseem-system-stats-manager.service 

You’ll need to wait for it to update in the Preseem interface. May take a day for it to update and start reporting.