When using VisualEditor, frequently seeing this:
JQMIGRATE: jQuery.fn.offset() requires an element connected to a document OO.ui.PopupWidget.computePosition OO.ui.mixin.FloatableElement.position
Not sure, but probably from this line:
https://github.com/wikimedia/oojs-ui/blob/bd15ed511c345db718dfdc6567224a6053e0fd36/src/widgets/PopupWidget.js#L502
Documentation
Release notes:
https://jquery.com/upgrade-guide/3.0/#breaking-change-invalid-input-to-the-offset-method
Migration legend:
https://github.com/jquery/jquery-migrate/blob/e967c3b98b/warnings.md#jqmigrate-jqueryfnoffset-requires-an-element-connected-to-a-document