Since 20:25 UTC, two ways around Cloudflare’s Free plan limits of one IP list and five custom rules.
/probes/cloudflare.csv is the probe list in the exact form Cloudflare’s Upload CSV takes, one «address, PingWise probe …» per line, IPv6 as each probe’s /64, updated with the fleet. Upload it into the list you already have and your existing rules let our probes through. Uploads never remove entries, so a retired probe’s line stays until you delete it.
Connect Cloudflare now has Use a list you already have. Pick one of your lists and we add our addresses to it, keep them current on every fleet change, change or remove only the entries we added, and create no rule. Our own list is deleted if we had made one, which frees the Free plan’s single list. The connection page shows which list is in use and when it was last updated, and Stop using this list takes our entries out again. Accounts with room keep the default: our list plus a skip rule per zone.
Thanks to Press Wizards for asking. Details on Probes and in the docs.