[adrienjarthon]

Quick update here: Vultr is still ignoring us, and Cloudflare said to one of my clients: "some IPv6 traffic from Vultr was being dropped by a DDoS mitigation system as we were receiving malicious traffic from Vultr. The issue has since been resolved, and updown should be reporting availability correctly now."

So this confirms what I suggested above, I suppose they choose not to respond with an HTML page here because it would generate too much traffic, and maybe it was a lower level TCP attack.

This also probably explains why Vultr doesn't want to answer me if they were "responsible" for the DDoS attack that got them blocked.