ipv 4 and 6

[Paul]

nginx/1.18.0 (Ubuntu).   For decades we have never explicitly "listened" 
for 1pv6, using only "listen 443 ssl;" on a couple of dozen websites.

As of two days ago, W3C (world wide web consortium) html, css, etc 
verification tools are no longer functional -- our websites "time out" 
"500 Can't connect to mysite.com:443 (Connection timed out)"

W3C have nslookup showing ipv4 and ipv6 addresses.  There is nothing in 
our firewalls "denying" them, there is nothing in the nginx logs.

I'm reticent to just add trillions of ipv6 possibilities of abuse (we're 
experiencing om/off ddos attacks from ai/automated/bots to the tune of 
56^6/day).

Any thoughts?

Thanks -- Paul