As of firmware 6.3 Peplink Routers can block traffic from specific applications. To begin navigate to Network > Firewall > Content Blocking (For MAX Devices: Advanced > Content Blocking).
Now add the following list of domains to the customized domains to block the the Youtube website + Youtube app:
Don’t forget to Save and Apply the changes and devices on your network won’t be able to view any YouTube content.
Note: Make sure you flush your dns settings between testing changes to avoid loading websites that have been cached already!
If you want to block entire categories of websites (e.g. media streaming, adverts), read about our list-based web-blocking feature 92.