How force HTTP/2 ?

Hi,

I'm using FreeNginx and in my configuration i have

 nginx

    
http2 on;

  

but when I make a vist on http://localhost/ it's http/1.1 that kick...

I've found^1

Firefox already has HTTP/2 AFAIK.The entry is called network.http.spdy.enabled.http2 but it's set to "false" by default,

I don't have this in LibreWolf, I created it, to see if it does something, but it's still the HTTP/1.1 that is used.. Any ideas ?

Thanks.