According to a GitHub issue, this appears to be due to archive.today refusing to remove illegal child pornography-related content in the EU. At present, other DNS resolvers like Control D, NextDNS, Google DNS do not seem to be blocking archive.today.
ameshkov, CTO of AdguardTeam, said:
The website hosts child porn and refuses to remove it when notified.
I am limited in what I can say on the matter until the legal procedures are resolved.
Let me put it like that: laws in some EU countries are changing in a way that can make technical intermediaries like a DNS service a legitimate target.
geofencing will be there a little bit later. The whole deal is quite unexpected so we weren’t fully ready.