Another Mullvad Integration Question

I'm hoping someone can help me out. I love using NextDNS on all my devices at home, and I'm also a big fan of Mullvad VPN. I've set up custom DNS servers in Mullvad, and everything works fine—except for one issue. When I have the VPN enabled, I lose the device name in the NextDNS reporting. It just records the IP. I've synced the VPN IP with NextDNS, and it works perfectly when the VPN is off (the device name shows up after I re-sync the IP).

Is there a way to keep the device name in the report while the VPN is on? It seems that Mullvad's custom DNS fields only accept the IP address without any additional parameters like the clientID.

I'm running Linux Mint and installed NextDNS using the curl method rather than editing the systemd-resolved file (though I did try that as well).

Any advice or suggestions would be greatly appreciated. Thanks in advance!