Cloudfare makes it weirdly difficult to find this. 1.1.1.1 is plastered over many pages but not concomitant with the secondary.
That is not my experience at all. By following the `install`-instructions on http://1.1.1.1, all available DNS addresses are listed for both ipv4 and ipv6.
That's not necessarily a bad thing, since it's probably better to use another source for a secondary if that's your primary.
I'm using cloudflare first, and google as secondary in my router. For a while I was running my own, but it became less necessary when I stopped doing as much dev at home.