Hi Gyori Balazs,
Thanks for contacting syncfusion support.
Query1: UWP does not show footer
We have prepared a sample based on your code. In the sample we were unable to reproduce the reported issue "UWP does not show footer" from our side. Please download the sample from the following link.
If the issue still persist, could you please provide more information like reproduceable steps. It would be helpful for us to proceed futhur on this.
Query2: Android stops with nullreference exception. FooterView is null.
We are able to reproduce the reported issue in the version 184.108.40.206. But the reported issue has been fixed in the latest version 220.127.116.11. Could be please download the latest version of essential studio and check the following issue. Please revert us if you face any issues.