No external data source plugin installed

I have just installed Nocobase on our local server.
When I try to Add a new data source there is a message “No external data source plugin installed”. However, the documentation says this plugin should be installed with the main code, there is no separate plugin for this. I checked the plugins manager, and couldn’t find one, just as stated.
Having external database connection is crucial to our use case.
What we did wrong?

External data sources are commercial plug-ins