Just set some of my recursors to DNS4EU, let's see how it performs!

https://www.joindns4.eu/for-public#resolver-options

First lesson: the modem/router provided by the ISP is utter garbage: you can't set DNS in DHCP options, but if you disable DHCP, it stops routing because DHCP config is the only way you can tell it about the IP range of the LAN