It's pretty unusual for ISPs to do this. But Spectrum is big enough that it's a still a valid concern.

Especially now that more and more people are using mobile networks from people like AT&T and Verizon, and these companies are effectively scum of the earth.

The real solution is to have the OS itself deal with DNS privacy concerns, not the browser. Localhost DNS resolver with DNSSEC enabled that will bypass the default DNS settings and go out to 'trusted' DNS servers when DNSSEC fails. Maybe even use DoH if ISP blocks normal DNS traffic.