Ask HN: How to report IP abuse to Cloudflare?

We are seeing aggressive abusive behaviour coming from 104.28.0.0/16 and 172.69.0.0/16 ranges directed at our web servers.

Emails sent to abuse@cloudflare.com bounce and Cloudflare's one and only online form requires an URL of a website that's involved in abuse ... which clearly doesn't apply here.

This looks absolutely ridiculous.

How to proceed?