Hi,
I think there is a little configuration error in the http server of manjaro.org.
The server responds to requests in HTTP (tcp/80) but reject requests to HTTPS (tcp/443).
As the HTTP redirects to HTTPS, the website in completely unreachable from a v6-only network (as mine).
You can check that with tools like internet.nl or mythic-beasts .
Can you fix that ?
Thanks 
Have to double check on how we redirect http to https on ipv6.
@ptitgnu can you try now again and let me know?
yep, It’s better
nginx listen now on tcp/443 and the website is reachable in v6 but the redirection from http to https doesn’t work anymore… (but only in v6 says the HTTPS redirect section on internet.nl ).
…and if I try to access to the website in http, I only see the “Welcome to nginx!” webpage.
Ok, I just tried this morning and the https redirection works too.
So it’s completely fixed now, thanks !
FYI: I’ve moved the solution to phil’s last remark as he implemented the solution.