My ISP currently makes them not resolve (with scary sounding domains):

  ; <<>> DiG 9.10.6 <<>> @192.168.1.254 annas-archive.li
  ; (1 server found)
  ;; global options: +cmd
  ;; Got answer:
  ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18716
  ;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1

  ;; OPT PSEUDOSECTION:
  ; EDNS: version: 0, flags:; udp: 4096
  ;; QUESTION SECTION:
  ;annas-archive.li.  IN A

  ;; ANSWER SECTION:
  annas-archive.li. 845 IN CNAME www.ukispcourtorders.co.uk.
  www.ukispcourtorders.co.uk. 511 IN CNAME ukispblk.vo.llnwd.net.
  ukispblk.vo.llnwd.net. 845 IN CNAME ukispblk.vo.llnwd.net.edgesuite.net.

  ;; Query time: 3 msec
  ;; SERVER: 192.168.1.254#53(192.168.1.254)
  ;; WHEN: Wed Feb 18 12:06:25 GMT 2026
  ;; MSG SIZE  rcvd: 169

Well, you get the warning, but as long as HSTS is not active, you can still click on "Accept the risk and continue" …

[EDIT:] Just checked a bit closer, they are using an LetsEncrypt cert for "cuii.telefonica.de", which is obviously the wrong domain, but as I said above, as long as HSTS is not active for "annas-archive.li", you can still bypass via the button.

It does. The browser won't load the content because it detects your connection was tampered with.

They redirect to a different url.

Your country's broken internet is your problem. If you are having DNS queries censored then change your DNS resolver on your client side. If you still get intercepted look into DoH.

Vodafone here seems more eager than other ISPs to block things, for some reason. I've had Telefonica, Orange, Jazztel and Movistar before and seemingly they weren't as eager, or there is a lot more blocking the last ~2 years which just happen to align with when we switched to Vodafone.

Sorry? I don't care what Cloudflare opposes, that half of the websites I use stop working during La Liga matches + Vodafone apparently goes above and beyond to block sites for knowledge sucks, regardless if CF or Trump are involved or not.

I can access it from both my mobile and fiber connections, different ISPs. I'm with smaller players so maybe that's it.

Implementation of this stuff must be very patchy then as both are off on my top 5 provider until I use a VPN. Which makes me wonder why any of the ISPs bother blocking at all, if they can just pick and choose?

I'm assuming BT? If so then their blocking is DNS based and if you are not using their DNS then they will block these sites