{ config, lib, pkgs, ... }:

{
  services.nginx = {
    enable = true;

    # Use recommended settings
    recommendedGzipSettings = true;
    recommendedOptimisation = true;
    recommendedProxySettings = true;
    recommendedTlsSettings = true;

    # Only allow PFS-enabled ciphers with AES256
    sslCiphers = "AES256+EECDH:AES256+EDH:!aNULL";

    # Setup Nextcloud virtual host to listen on ports
    virtualHosts = {

      ### Nextcloud
      "docs.tompurl.com" = {
        ## Force HTTP redirect to HTTPS
        forceSSL = true;
        ## LetsEncrypt
        enableACME = true;
      };

      ### Synapse
      # This host section can be placed on a different host than the rest,
      # i.e. to delegate from the host being accessible as ${config.networking.domain}
      # to another host actually running the Matrix homeserver.
      "destrocodpiece.wtf" = {
        enableACME = true;
        forceSSL = true;

        locations."= /.well-known/matrix/server".extraConfig =
          let
            # use 443 instead of the default 8448 port to unite
            # the client-server and server-server port for simplicity
            server = { "m.server" = "matrix.destrocodpiece.wtf:443"; };
          in ''
            add_header Content-Type application/json;
            return 200 '${builtins.toJSON server}';
          '';
        locations."= /.well-known/matrix/client".extraConfig =
          let
            client = {
              "m.homeserver" =  { "base_url" = "https://destrocodpiece.wtf"; };
              "m.identity_server" =  { "base_url" = "https://vector.im"; };
            };
          # ACAO required to allow element-web on any URL to request this json file
          in ''
            add_header Content-Type application/json;
            add_header Access-Control-Allow-Origin *;
            return 200 '${builtins.toJSON client}';
          '';
      };

      # Reverse proxy for Matrix client-server and server-server communication
      "matrix.destrocodpiece.wtf" = {
        enableACME = true;
        forceSSL = true;

        # Or do a redirect instead of the 404, or whatever is appropriate for you.
        # But do not put a Matrix Web client here! See the Element web section below.
        locations."/".extraConfig = ''
          return 404;
        '';

        # forward all Matrix API calls to the synapse Matrix homeserver
        locations."/_matrix" = {
          proxyPass = "http://[::1]:8008"; # without a trailing /
        };
      };
    };
  };
}

In reply to @tompurl:destrocodpiece.wtf
Good morning f0x . I just wanted to thank you again for your quick help. I'm now am able to join this room with my "real" account using my very own homeserver.