I just setup Cloudflare for Teams, and it was fairly easy to get it working with Cloudflared on my PiHole (DOH). Cloudflare for Teams is a customizable version of their DNS (among other features). I was able to get a free account there, and received a unique URL (ip number won't work - must use URL) to use for DOH. Then I was able to go in and specify categories of sites that I want blocked. I was mostly interested in blocking malware. I'm hoping this is redundant to what I already have in my PiHole, but it also very possible that Cloudflare will identify some things I don't have in blocklists.
Install: I already had Cloudflared installed according to fine instructions in docs.pihole.net. I edited /etc/default/cloudflared and changed " --upstream https://1.1.1.1/dns-query --upstream https://1.0.0.1/dns-query" to "--upstream https://kmixxxxxx.cloudflare-gateway.com/dns-query" (unique to your account). Then I restarted Cloudflared, and checked status. Lastly, I went to "1.1.1.1/help" to confirm DOH was on.