It is not too difficult to allow your PiHole to serve you globally (but does requiring opening some ports in your firewall == additional security risk).
There is a simple checkbox within the DNS's web interface to `Allow WAN Requests`. You'd then only run into issues of accessing your local IP addresses if those hosts aren't configured correctly within your network rulesets.
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I am a user, not an expert; by trade, I am a blue collar electrician. I know very little about internet topology except how to use simple open-source hardware. Perhaps what you said makes sense (e.g. that you cannot use outside your network, some service(s)).
Yeah that can work, though at that point I start to consider just exposing my "internal" DNS to the world at large - who cares if secret_service.mydomain.net can be seen by everyone to resolve to 192.168.88.4?
I think my major concern here would be if people were going to websites which might be considered illegal within their jurisdiction (e.g. guest_DNS_user searches for out of state abortion providers — while you[r DNS] live[s] in Texas).
Perhaps the State sees guest_DNS_user's query to plannedparenthood.com, then decides your vehicle tag is worth tracking for potential out-of-state (via e.g. Flock cameræ)... or that you are guilty of facilitating an abortion for someone else... all because your DNS server provided IP resolution for guest_DNS_user to Planned Parenthood Colorado (et.al).
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This would have been too far-fetched for me to have considered/written, even just a few years ago. It's all reality, now. Are you targetable enough?
DNS leaks are another reason I don't care for LittleSnitch (which pre-resolves IP address before the accept/deny pop-up even appears.
I have setup a VM running DNS on my laptop before ...