I've experienced this on both my private VPN (self hosted on a VPS) and even on some public WiFis, I can think of the SNCF trains in France for example. Is there anything the admins could do about it? (sorry for the ping IBJoel) or should I contact Cloudflare? (their error page says to contact the site admin so I'm coming here first).

It's the only site I can think of that's this protective but I know security is always a difficult balancing act.