I'm a noob, but.. there definitely seems to be something wrong.
I had DoH working with 1.1.1.1.
Then I decided to dabble with a PiHole.
I set my DNS to the PiHole and press Apply... great, everything works!
...a dayish later?...
I'm back to resolving via Verizon. TL;DR if I goto the webfig page for DNS and simply press Apply -- leaving the existing server IP as-is -- then boom, all my clients are using my pihole again.
For about a dayish.