The lua.org website is unreachable over IPv6 (2a01:4f8:201:620f::2).
The www.lua.org domain, however, has a different IPv6 address and seems
to work as intended. Any chance that the www-less domain is simply
$ curl -6 -v https://lua.org/
* Trying 2a01:4f8:201:620f::2...
* connect to 2a01:4f8:201:620f::2 port 443 failed: Connection refused
* Failed to connect to lua.org port 443: Connection refused
* Closing connection 0
curl: (7) Failed to connect to lua.org port 443: Connection refused