The Horde webmail application has been removed in cPanel & WHM version 108 (at the time of writing we are on the latest stable release 106.0.13). All Horde email, contacts, and calendars will be automatically migrated to Roundcube.
For more information, read our cPanel Deprecation Plan documentation here – https://docs.cpanel.net/knowledge-base/cpanel-product/cpanel-deprecation-plan/#