Due to the inaccessibility of OpenDNS in France following a court decision (Blog Stéphane Bortzmeyer: OpenDNS plus accessible depuis la France), I tell myself that it is perhaps better to delete it from the list of services offered?
People using this service from France will say that there is a problem with Pi-hole when it's just that OpenDNS no longer responds to French IPs.
The primary source (in French) is Article L333-10 - Code du sport - Légifrance. It is unclear to me whether France authorities blocked access to OpenDNS altogether or if was OpenDNS's own decision to not serve content for French users any longer as they refuse to accept the selective DNS blocking ordered by the French sport court.
As I'm not based in France myself, I cannot test either theory but - as OpenDNS themselves provide virtually no information either, I tend to lean to towards the latter.
Similar things happened before and seem to have gone away shortly after so I'm not really looking forward to removing OpenDNS yet.
Concerning DNS4ALL: They describe themselves as in "beta" - doesn't sound like we want to add them (yet) either.
I hadn't seen the mention that the service was in beta, which is big though...
I hope they will settle permanently, because we lack trusted and neutral DNS...
I hope you are right about OpenDNS.