Introduction
When LiteSpeed is installed on a cPanel & WHM server, QUIC is turned on by default for Apache HTTPS vhosts. All that is required is to open UDP port 443.
However, it is possible to disable QUIC for all domains on the server. Alternatively, it can disabled for only specific domains and virtual hosts.
Procedure
Disable for QUIC for all domains on the server:
To disable QUIC for the server, you must edit the file /etc/apache2/conf.d/includes/pre_main_global.conf and add the following information:
<IfModule LiteSpeed>
QuicEnable off
</IfModule>
Then rebuild the configuration and restart the LiteSpeed service using the command below:
/usr/local/cpanel/scripts/rebuildhttpdconf && /usr/local/cpanel/scripts/restartsrv_apache
Disable QUIC for one Domain/Virtual Host:
To disable QUIC for one domain, or virtual host, you must create a quic_vhosts.conf file for the domain. For the non-SSL version of the domain you would need to create the directory:
/etc/apache2/conf.d/userdata/str/2_4/$user/$domain/
Then for the SSL version of the domain you would create the directory:
/etc/apache2/conf.d/userdata/ssl/2_4/$user/$domain
(Please replace $user with your cPanel account username, and $domain with the domain where QUIC should be disabled.)
Then within each of those directories, create the file: quic_vhosts.conf - The file should contain the below data:
<IfModule LiteSpeed>
QuicEnable off
</IfModule>
Then rebuild the configuration and restart the LiteSpeed service using the command below:
/usr/local/cpanel/scripts/rebuildhttpdconf && /usr/local/cpanel/scripts/restartsrv_apache