Ghacks' post [1] has a good summary of related links and an active discussion at comments section, though the "protection" got more strict in the meantime thus the mentioned workaround isn't effective anymore.

Some users have posted at Clodflare community forum to no avail and Cloudflare support is only available to paid customers. Visitors are told to contact respective web site owners and forum threads are locked quickly.

Let me be clear, this is not a case of a web site owner deciding to use a recent feature that's not supported by these browsers. That'd between visitors and owners of that web site, and completely understandable.

This is a serious issue. A 3rd party corporation is deliberately deciding which browsers are legitimate and which are not. They prevent users of these browsers from accessing millions of websites with a flip of a switch. There's no transparency and no accountability to their actions.

I hope this issue will be heard, fixed and never be repeated again.

[1] https://www.ghacks.net/2022/05/05/fix-pale-moon-browser-not-passing-cloudflares-checking-your-browser-verification/

Other links: https://github.com/WaterfoxCo/Waterfox-Classic/issues/107