Anubis flatly refuses me access to several websites when I'm accessing them with a normal Chromium with enabled JS and whatnot, from a mainstream, typical OS, just with aggressive anti-tracking settings.

Not sure if that's the intended use case. At least Cloudflare politely masks for CAPTCHA.

What do you mean "refuses"? The worst it should do is serve up a high difficulty proof of work. Unless it gained new capabilities recently?

Are you sure the block isn't due to the authors of those websites using some other tool in addition?

I thought that Anubis solely is proof of work, so I'm very curious as to what's going on here.