The date picker cannot be opened on Safar: when you click the datebox, the picker popup appears and disappears quickly, it is almost impossible to use it. The behavior is the GMD demo: https://gwtmaterialdesign.github.io/gmd-core-demo/#datePicker
The picker popup cannot be shown on the screen - if it located inside a container with overflow auto or hidden, it will be cut off. This does not happen on Chrome, it works correctly there.
If I set the picker container as the document BODY, and then try to use the MaterialDatePicker in GWT a popup (for example a form in a modal popup with "glass"), the picker popup is displayed, but no element inside it can be clicked and neither it can be dismissed at all