They could block all outgoing traffic to port 53, although you could work around that by setting up a DNS server on a different port outside the network
Vodafone Kable, so YMMV.
Always a bit scared to switch providers of course, you never know if you get cgnat and blocked DNS servers. They are building a Deutsche Telekom fiber to our street this summer. It's tempting for the 200 Mbps uplink, But I have no idea is it then CGNAT and do they even provide real IPv6. It's never mentioned in the advertisement.