Just a minor suggestion:
While I appreciate the consistency in always loading the left most tab when navigating to a new page, I would especially appreciate either a stateful tab focus that opens the tab that was open when last the page was exited.
Otherwise, as is especially the case in the Services: DHCP server and Firewall: Rules, loading the most likely tab to be needed which would be the LAN tab in those cases.
Nitpicky and detail oriented, I know. If I knew how to make that happen, I would readily provide the patches.
Thank you again for all the great work.