Active directory server default gateway resolution issues

I am using a Raspberry Pi 2 running Ubuntu Server acting as an active directory domain controller with samba and kerberos etc as detailed in [this video](https://www.youtube.com/watch?v=tgBuvA6J-_8) . I have three Windows 11 Professional clients part of the domain. The clients are configured with their own IP address, use the same network-wide subnet mask, and dns settings are routed to the dc, with the secondary (alternative dns server) as the default wifi router (as a device off the network domain would use). In the video, it shows changing the default gateway of the windows clients to the IP address of the DC. I made this change, and connected to the domain successfully. However, when performing basic searches or accessing external sites online on the clients, it is EXTREMELY SLOW or fails to load even the simplest page. If I change the default gateway of the client back to the router IP address (as it would have been originally), then the webpages load completely fine, however, the client loses the domain entirely, and doesn't even recognise it as existing. E.g. a ping to exampledomain.local doesn't reach. **Is there a way to remain part of the domain, in touch with the DC, whilst using the gateway of the router on the clients?** Very new to all this, including IT forums etc, so feedback on my question appreciated.