I was using safari on the iPad with the Purify ad blocker extension, but I run Purify on the iPhone I’m posting this from right now as well (but on cellular rather than my home wifi). I did log in both in the web interface and in the iOS app “mlem” in short succession though - maybe that triggered some security response.

Same here. I’m a brand new user as of today and the ban suddenly happened a few minutes after first login on my home network, as I was subscribing to communities that seemed interesting to follow. After having clicked subscribe on like 5-10 communities the clicks on the subscribe link just started timing out, and then I got the crowdsec ban page when I tried to reload the page.