Test Suite collection not communicating with BrowserStack

We have a Test Suite Collection that worked fine with Browserstack (from both, our windows and linux machines), until we switched to local mode of Browserstack.
In the local mode, the collection still works when run from my local Windows PC (Katalon 6.1.4).
But no interaction is visible on Browserstack, when the collection is run from a docker image (Katalon 6.1.1) on the linux machine.

I would be grateful for a hint how to make the Browserstack aware of the running tests.

It was sufficient in the remote connection specification to change the type of the browserstack.local variable from the incorrect type String to Boolean.

(Project > Settings > Desired Capabilities > Custom > …)

For some reason the wrong type String was not a problem on Windows, only when the test was run in the CI/CD environment on Linux.