Earlier quoted context omitted.
Copying my previous comment over because I found a fix that works for me: There's some issue with DNS over HTTPS, so you have to whitelist their sites in your settings, or turn off DNS over HTTPS (which I don't recommend). To whitelist, on Firefox: Hamburger menu > settings > privacy and security > DNS over HTTPS > Manage exceptions > Add "archive.is", "archive.ph", and "archive.today"
It has nothing to do with dns-over-https, it has to do with using cloudflare dns at all, over https or plain. In my case I added override rules in my opnsense router so that archive.is .ph .today .md are all resolved by a different nameserver. Disabling DOH can appear to fix it only in the happenstance case that the fallback plain dns doesn't end up using cloudflare, or doesn't use it first.
https://mullvad.net/en/help/dns-over-https-and-dns-over-tls/
No issues with any archive-sites.
Aside from not being censored at all, thereby enabling visiting sites which are blocked at DNS-level in some locations, there are several options for adblocking at DNS-level, too. Often eliminating the need for a Proxy or VPN to get access, with optional Adblock as a service.
For free.
It's nice.