Empty GeoJSON for line geometry

I created a simple form to test tohe capacity to record line geometries.
The CSV export shows me it seems to work:

but CSV is not a useful format for line geometries so It ried to export the same data in this format, but the file is completely empty:

Is it a bug? Is there another way to get around this?

Welcome back to the community, @Severin! What was the question type you used for this? Maybe I could test it at my end too.

The Line type, of course