And it isn't like anyone needs to modify DHCP standards to support this. Just use any of the "options" text to add DoH/DoT, the same way browsers are advised of PAC URL's today. Only the clients would need updates to know how to use this, and adding the capability to an OS should be fairly easy to implement.

  option wpad-url code 252 = text;
  option wpad-url "http://10.10.10.10/proxy.pac\n";

I'm sure there is a clean way to overload or augment this capability to extend it to DoH/DoT.

I did something similar for a PoC at my university. It worked, no surprise there. All you need to do is have a another client script in Debian to configure your resolver.

I should add that DoH developers should reach out to ISC for comment on DHCP, to get an idea what the cleanest method would be to implement DoH/DoT in DHCP that would work for 90%+ of DHCP implementations.