how to enable http/2 on apache2 using ubuntu 20.04?

I have VPS server running ubuntu 20.04 (apache2) and is using http/1.1 and I want to upgrade to http/2

The domain is already configured using v-hosts (and has the ssl installed - lets encrypt).

Testing the current protocol:

$ curl -I https://my-domain.com
HTTP/1.1 200 OK
Date: Fri, 12 Mar 2021 17:32:01 GMT
Server: Apache/2.4.41 (Ubuntu)
Content-Type: text/html; charset=UTF-8

Steps that I done to upgrade to http/2:

1) sudo a2enmod http2

2) add in virtual host (ex: /etc/apache2/sites-enabled/my-domain.com-le-ssl.conf) the line:
Protocols h2 http/1.1     

3) check the config
sudo apache2ctl configtest

4) Restart the web server
sudo systemctl reload apache2

Test again the ptotocol:

$ curl -I https://my-domain.com
HTTP/1.1 200 OK
Date: Fri, 12 Mar 2021 17:57:07 GMT
Server: Apache/2.4.41 (Ubuntu)
Upgrade: h2
Connection: Upgrade
Content-Type: text/html; charset=UTF-8

As you can see it still using the http/1.1

What did I miss ???

UPDATE

apache2 loaded modules

 $ sudo apachectl -M
 Loaded Modules:
 core_module (static)
 so_module (static)
 watchdog_module (static)
 http_module (static)
 log_config_module (static)
 logio_module (static)
 version_module (static)
 unixd_module (static)
 access_compat_module (shared)
 alias_module (shared)
 auth_basic_module (shared)
 authn_core_module (shared)
 authn_file_module (shared)
 authz_core_module (shared)
 authz_host_module (shared)
 authz_user_module (shared)
 autoindex_module (shared)
 deflate_module (shared)
 dir_module (shared)
 env_module (shared)
 expires_module (shared)
 filter_module (shared)
 headers_module (shared)
 http2_module (shared)
 mime_module (shared)
 mpm_prefork_module (shared)
 negotiation_module (shared)
 php7_module (shared)
 reqtimeout_module (shared)
 rewrite_module (shared)
 setenvif_module (shared)
 socache_shmcb_module (shared)
 ssl_module (shared)
 status_module (shared)

php 7.4.3 installed

php 
libapache2-mod-php 
php-mysql 
php-cli 
php-mbstring 
php-imagick 
php-xml 
php-gd 
php-zip 
php-curl 
php-opcache 
php-soap 
php-bcmath

vhost config:

<VirtualHost *:80>
    ServerAdmin [email protected]
    ServerName my-domain.com
    ServerAlias www.my-domain.com
    DocumentRoot /var/www/my-domain.com/public

    Protocols h2 http/1.1 

    <Directory /var/www/my-domain.com/public/>
    Options Indexes FollowSymLinks MultiViews
    AllowOverride All
        Require all granted
    </Directory>

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
RewriteEngine on
RewriteCond %{SERVER_NAME} =my-domain.com [OR]
RewriteCond %{SERVER_NAME} =www.my-domain.com
RewriteRule ^ https://%{SERVER_NAME}%{REQUEST_URI} [END,NE,R=permanent]
</VirtualHost>

and the ssl config:

<IfModule mod_ssl.c>
<VirtualHost *:443>
    ServerAdmin [email protected]
    ServerName my-domain.com
    ServerAlias www.my-domain.com
    DocumentRoot /var/www/my-domain.com/public

    Protocols h2 http/1.1 

    <Directory /var/www/my-domain.com/public/>
    Options Indexes FollowSymLinks MultiViews
    AllowOverride All
        Require all granted
    </Directory>

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined

    Include /etc/letsencrypt/options-ssl-apache.conf
    SSLCertificateFile /etc/letsencrypt/live/my-domain.com/fullchain.pem
    SSLCertificateKeyFile /etc/letsencrypt/live/my-domain.com/privkey.pem
</VirtualHost>
</IfModule>

UPDATE 2

What I found in the error.log (apache)

[http2:warn] [pid 507] AH10034: The mpm module (prefork.c) is not supported by mod_http2. The mpm determines how things are processed in your server. HTTP/2 has more demands in this regard and the currently selected mpm will just not do. This is an advisory warning. Your server will continue to work, but the HTTP/2 protocol will be inactive.

Probably this is the reason. Maybe using mpm_event instead of mpm_prefork will work.

I am not sure if I need the php-fpm...

1. Replacing the mpm_prefork with mpm_event
2. using php-fpm (libapache2-mod-fcgid) instead of (libapache2-mod-php)

solve the problems.

The credit goes to @MichaelHampton!