Dovecot following the enshittification handbook
Dovecot new version 2.4 is a breaking change from 2.3 and deliberately so. With version 2.4 the paid Pro version does have all functionality and some from 2.3. The new Community Edition is only usable for a single server without high availability or cluster functionality.
To make sure you break everything the config files from 2.3 and 2.4 are not (backward) compatible. And to make this move even more profitable you will not find a pricing scheme anywhere you have to ask a quotation for your specific configuration.
Time to fork the current 2.3 version.