Seems like the URL property is not used as a general-purpose field, but its purpose is:
This property may be used to convey a location where a more dynamic rendition of the calendar information can be found.
the whole thing is working fine on arch-linux using gnome shell!
Would it be possible to have a picture of the screen on the Android device?
Maybe it doesn’t need to be a live-view. Only a screenshot for orientation could be a very nice feature to draw on.
We’ll try to incorporate something like that in the future! Thank you for the suggestion