Link to External Data menu missing in Calc

In my latest CODE installation (Docker Hub: collabora/code:6.4.6.8) I am not able to query external URLs with Calc.

Using =WEBSERVICE() function results in an error message: Err:540 for any URL. The status bar at the bottom indicates External content disabled.

Following the Inserting External Data in Table (WebQuery) guideline I do not see the Link to External Data icon/button on the Sheet tab.

Any ideas?