Barracuda Web Security Gateway
Why are my chromebook users not seen as a domain user?
Anwer:
The setup needs to incorporate GADS or GAPS to work correctly
https://campus.barracuda.com/product/websecuritygateway/article/BWF/ChromeSecExt/
If you do not configure GADS/SSO, you can create local users with matching usernames, which will automatically match users coming from the google domains.