If you're wondering, I'm on Firefox connected thru Google Fiber. I've tried disabling Enhanced Tracking Protection, but all that does is make it so I don't have to solve a captcha. I still get the endless loop of challenge pages.
As I understand it: the technical cause is that the Archive.is authoritative DNS server refuses to respond correctly to requests without EDNS subnet information, and Cloudflare’s resolver refuses to send requests with it. (Cloudflare says this is for privacy reasons, and I believe Archive.is says their response is for legal reasons.) The captcha loop seems to be a recent development; apparently[2] it’s not actually from Cloudflare, just styled to look like it.
[1] https://jarv.is/notes/cloudflare-dns-archive-is-blocked/
https://developers.cloudflare.com/1.1.1.1/privacy/cloudflare...
> To counter such threats, Mozilla has partnered with Cloudflare to provide direct DNS resolution from within the Firefox browser using the Cloudflare Resolver for Firefox. What this means is that whenever you select or type a web address in the Firefox browser your DNS lookup request will be sent over a secure channel to the Cloudflare Resolver for Firefox rather than to an unknown DNS resolver, significantly decreasing the odds of any unwanted spying or man in the middle attacks.
(Plus, since last month, Cloudflare no longer has captchas at all: https://news.ycombinator.com/item?id=37799413)