Subject: WireGuard VPN – DNS resolution issue for internal network

I am experiencing a DNS resolution issue when connected through a WireGuard VPN hosted behind a UniFi UDM SE.

Environment:

VPN: WireGuard (configured on UniFi UDM SE)
Client: WireGuard (latest version)
Internal DNS server: 192.168.1.197 (Active Directory / Windows Server DNS)

Current behavior:

The VPN connection is successfully established.
I can access the internet without any issue through the VPN.
I can ping and reach all internal network devices using their IP addresses.
However, I am unable to resolve or ping hostnames of machines on the internal network.

Example:

ping 192.168.1.xxx → OK
ping server-name → Failed (name not resolved)

Additional details:

The DNS server configured in the WireGuard client is correctly set to: 192.168.1.197
The DNS server is reachable over the VPN (ping OK)
The issue only affects hostname resolution (DNS)

Expected behavior:

Internal hostnames (Active Directory domain) should resolve correctly when connected to the VPN.

Could you please help identify what might be missing or misconfigured (DNS forwarding, routing, or WireGuard settings)?