[Bug] AppTP incompatible w/ some private DNS providers

[laghee]

Describe the bug

NextDNS in particular has been cited as conflicting with AppTP, but there have also been intermittent issues with, e.g., quad9. Users have reported issues with no trackers being blocked by us and/or connectivity issues in general.

Cloudflare one.one.one.one seems to work without issue, however.

How to Reproduce

1. Go to Settings -> Network & Internet (Pixel) -> Private DNS
2. Switch to "Private DNS provider hostname" & add server OR install provider's app
3. Enable AppTP from DDG browser settings

(Internal task link )

Expected behavior

Ideally, AppTP could at least coexist with a private DNS provider (though obviously if they are already blocking most requests, we still wouldn't show much, if any, activity).

Environment

- DDG App Version: including 5.143.1
- Device: Varied
- OS: Varied

[madduck]

I run my own private DNS and it's impossible to use alongside the vpn. If I can help debug, I'd love to!