If you disable IPv6 (systemwide) you must comment or remove the IPv6 references in /etc/hosts.
I did some troubleshooting on NordVPN a few days ago - a DNS issue I didn’t bother to troubleshoot earlier - and found that switching resolver from the default (openresolv) to systemd-resolved fixed my DNS issues.
Now I cannot guarantee anything - but I reckon it is worth a try 