We installed Web AppBuilder and hooked it up to our local Portal installation and built a test app.
We used these two documents to do so:
https://developers.arcgis.com/web-appbuilder/guide/getstarted.htm
https://developers.arcgis.com/web-appbuilder/guide/build-your-first-app.htm
If I edit the test app the widgets I assigned to be in the test app show up. If I Launch the test app from within Web AppBuilder, the widgets also show up.
When I use the browser debugging tools to track what calls are being made over the network, I see calls like this for widgets:
myserverUrl/widgets/Search/manifest.json?wab_dv=2.3
