Yesterday I learned that Virgin Media is inserting itself into some of my DNS requests. Much as I am not a fan of how powerful Cloudflare are, if they are telling the truth about their DNS, then it’s safe, so I followed their instructions on how to use their DNS and then removed the default DNS and hopefully my Internet will work now.
From the serverfault answer by lauc.exon.nod:
nmcli con mod "Wired connection 1" ipv4.dns "1.1.1.1 1.0.0.1" nmcli con mod "Wired connection 1" ipv4.ignore-auto-dns yes nmcli con down "Wired connection 1" nmcli con up "Wired connection 1"
If your router supports it, I would recommend to use DNS over TLS if you can as that’ll make it much harder for your ISP to intercept/modify DNS queries.
Agreed with Timo above, the term ‘hijack’ is because they go to every measure to ignore the setting on your devices by reinjection of their DNS by force even if the device is configured as you detail. The ONLY way to avoid this is to use encrypted DNS ie DNS over TLS or DNS over HTTPS.