https://www.nginx.com/blog/nginx-1-13-9-http2-server-push/ We’re delighted to announce that NGINX 1.13.9, released on February 20, 2018, includes support for HTTP/2 server push. We should be able to enable it by enabling --with-http_v2_module parameter Thanks
https://github.com/gentoo/gentoo/blob/master/www-servers/nginx/nginx-1.19.0-r1.ebuild#L466