A browser's (Chrome) DescribeFeatureType request to GeoServer version 2.12 returns an inline XML response in the browser's window.
Using that same browser to send a DescribeFeatureType request to a GeoServer version 2.14, the response is a document that is downloaded to the Windows' Downloads directory with the filename
geoserver-describefeaturetype.application. This document contains the same XML content as the inline XML response when requesting from GeoServer version 2.12.
Coincidently, QGIS is not able to resolve the DescribeFeatureType request to the GeoServer version 2.14 but does resolve the DescribeFeatureType request from GeoServer 2.12.
We don't see any settings in GeoServer to modify how it responds to DescribeFeatureType requests.
Interestingly, a browser's GetCapabilities request to both versions of GeoServer yields an inline XML response from GeoServer.
The DescribeFeatureType request is in the form
and the GetCapabilities request is in the form
Most importantly, we want to get the WFS connection from QGIS to GeoServer version 2.14 working. But we also want the inline response to a DescribeFeatureType request.