It is important to note that there are TWO SymmetricDS Docker images: one open-source and another for the PRO version (paid license). https://hub.docker.com/u/jumpmind

The open-source SymmetricDS Docker image depends on YOU to provide details of database connection in the .properties engine file (as described in the User guide). So this is working as designed. https://symmetricds.sourceforge.net/doc/3.15/html/user-guide.html

The PRO version of SymmetricDS has many more features, including a web console UI. This image works out of the gate and allows web console user to configure all database connections (multiple if you wish), provide license details and reboot to apply changes. https://downloads.jumpmind.com/symmetricds/doc/3.15/html/user-guide.html