User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:104.0) Gecko/20100101 Firefox/104.0

Steps to reproduce:

Enable DoH
Try to access a website that resolves in the RFC1918 range

Actual results:

"Server not found" page

Expected results:

At least, have a better reporting for this kind of error, I have spent days wondering why I couldn't access a corporate website on Firefox only, until I found network.trr.allow-rfc1918 by accident.

Better yet, it would be nice to be able to whitelist domains, so that it's not an entirely on/off protection.

The Bugbug bot thinks this bug should belong to the 'Core::Networking' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.