How can I isolate VPN client DNS quiries from server ?

Hello !

VPN server:

• Linux on VPS

• Wireguard server

• Fixed, global in /etc/systemd/resolved.conf: DNS = Trex

VPN client:

• Linux desktop

• Wireguard client

• Fixed, global in /etc/systemd/resolved.conf: DNS = NextDNS-ID

Opening ipleak.net in client browser, it finds both Trex and NextDNS. So, not all DNS queries from a desktop computer go to NEXTDNS some hits goes to trex.

My goal would be to have everything coming from the client use ONLY the client's DNS records (NextDNS) and everything else the server's DNS records (Trex). So ipleak.net in client browser must show only NextDNS.

I cant't write my NEXDNS-ID records to the VPN server, because someone else from my family uses another ID in their device.

How can I isolate VPN client DNS quiries from server ?

Any ideas ? Thanks !