Our Popups include an attribute (Associations) that's based on a custom expression (which forms a URL). It displays correctly in ArcGIS Pro and in Portal when the feature with the Popup is selected AND when the Popup is used for displaying a Search result. However, when we use it for displaying Query results, the full Popup does not display. Specifically, the custom expression is missing.
The expression (arcade) for the Associations attribute is as follows:
The help docs for the Portal Query Widget indicate (at 13):
'Check Use layer's pop-up configuration in the web map if you want to show the same content defined by the layer’s pop-up configuration in the web map.'
But in this case, the content isn't the same because of the missing Associations attribute.