Ubuntu 22.04
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Apache2 : Configure mod_http2
Configure [mod_http2] to use HTTP/2.
Configure SSL/TLS settings, refer to here.
(many Web browsers support HTTP/2 only on HTTPS connection)
[2] Configure [mod_http2].
It's possible to set it for each virtual hostings.
# configure [mod_http2] to any virtual host sites you'd like to set

vi /etc/apache2/sites-enabled/dlp.srv.world.conf
# add [Protocols ***] line

<VirtualHost *:443>
    Protocols h2 http/1.1
    DocumentRoot /var/www/dlp
    ServerName dlp.srv.world:443
    ServerAdmin webmaster@dlp.srv.world
    ErrorLog /var/log/apache2/dlp_ssl_error_log
    CustomLog /var/log/apache2/dlp_ssl_access_log combined
    SSLEngine on
    SSLCertificateFile /etc/letsencrypt/live/dlp.srv.world/cert.pem
    SSLCertificateKeyFile /etc/letsencrypt/live/dlp.srv.world/privkey.pem
    SSLCertificateChainFile /etc/letsencrypt/live/dlp.srv.world/chain.pem

<Directory "/var/www/dlp">
    Options FollowSymLinks
    AllowOverride All
    Require all granted

a2enmod http2

Enabling module http2.
To activate the new configuration, you need to run:
  systemctl restart apache2

systemctl restart apache2
# verify accesses
# OK if [HTTP/2] is shown

curl -I https://dlp.srv.world/

HTTP/2 200
last-modified: Thu, 01 Sep 2022 00:47:10 GMT
etag: "29af-5e792f41ed553"
accept-ranges: bytes
content-length: 10671
vary: Accept-Encoding
content-type: text/html
date: Thu, 01 Sep 2022 00:49:39 GMT
server: Apache/2.4.52 (Ubuntu)
  It's possbile to see HTTP/2 in response header from Web browser access. The example below is on Google Chrome.
If HTTP/2 is enabled, [Protocol] in response header turns to [h2] like follows.
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