Hi Gabriel,
Thank you for contacting Syncfusion support.
We have already found and fixed this mentioned issue “Popup doesn’t render in full screen” in Xamarin.Forms. This issue fix will be included in our upcoming Volume 1 Service Pack release which is expected to be available by next week of May 2019. We will let you know once it has been rolled out and appreciate your patience until then.
Regards,
Subburaj Pandian V