hCaptcha is pretty darn good in stoping bots as well. I recommend of thinking for this variation also. As I said, Google does not stop bots effectively anymore ( they hack accounts soo capcha is just another destroyed thing of google )

Do you have case study that would prove this?

Yes. I am having. For years my clietns (and me ) are using Your themes and plugins bought from you They all have the classic Captcha and some have also the Anti-Spam & Bot Protect Plugin. Those without the anti spam pluugin do have way more bots and bot registrations and ads, those with the antispam have less, but it also pases bots ( mostly ones using gmail.com emails). The hCaptcha I am using on a lot ow Wordpress ( as also the other proposed feature request for cludflare captcha ) and they work a lot better than Google's captcha or invisible captcha. Actually I am thinking that Google's things almoust ....dont work I know it sounds weird, but websites using it are flooded with or without them. They seems to ..slow down atacks slightly but... thats it. Now when i restrict by emai providers is good. The problem is when busines owners want to register iwth their business emails ( domain emails ) they cant, because I have only st up few email providers to be allowed on most of clients websits that are using the anti-spam plugin

I see, we will try to analyse this