[reify]

I personally do not visit any site with a captcha.

I dont play silly games.

However, in the past I have noticed that some addons prevent the completion and create a continual loop.

disable each addon if you use them one at a time to see if that makes a difference.

you dont say which OS you are using.

If you are not tech minded install bleachbit and run that to clear out all the hidden rubbish in .cache etc.

[Mateon1]

I'm using Windows on this laptop, this seems to affect all sites with any sort of Cloudflare protection, including Cloudflare's support and discourse sites, pubs.acs.org, and annoyingly some sites necessary for my current projects, that I need to access daily.

To clarify, this is the "Verifying your connection is secure" captcha before the site is even displayed, not a reCAPTCHA after the site is loaded.

I've tried clean browser profiles with no difference, on my normal profile I just use uBlock, Tree Style Tabs (FF)/Tabs Outliner (Chrome), and Tampermonkey for some sites (but not the ones affected by the captcha loop, in this case).