Regarding the Pi-Hole issues... a few days ago, I decided to set up firewall rules to block all outgoing DNS and DNS-over-HTTPS traffic, except one coming from my Raspberry Pi. I discovered two things:
My nVidia Shield TV was desperately trying to connect to Google's DNS. So yeah, I wasn't being paranoid!
My phone's Google Play Store refused to work without using Google's DoH. That's the troublesome side effect if DoH.
Generally to check I just use Wireshark, but if they're big enough (Google), they'd probably talk about it. Also, ESNI isn't even the default in Firefox, and it's just straight up not implemented in Chrome.
My nVidia Shield TV was desperately trying to connect to Google's DNS. So yeah, I wasn't being paranoid!
My phone's Google Play Store refused to work without using Google's DoH. That's the troublesome side effect if DoH.