There are those who wish to do away with IPv4 and use solely IPv6. How, then, does one connect to the router? The default URL is http://192.168.1.1, which is IPv4.
Well, there’s a way.
Go into the connection stats for your computer and get your IPv6 IP address.
Mine is :
fdf8:6213:46ff::a9c
Change the last bit after the last colon to a 1 :
fdf8:6213:46ff::1
Wrap that in square brackets :
[fdf8:6213:46ff::1]
Add the http:// or https:// :
https://[fdf8:6213:46ff::1]/
… put your version of that into your browser address bar, hit Enter, and the LuCI interface will come up.