We have assembled for testing a single ArcGIS Enterprise 10.5 server with all three components (Server, Portal, Data Store), and with the Server federated to the Portal. We already have a Portal in production, so we are familiar with it, but we have no experience with federation until this test configuration.
Here's a problem I have encountered during testing: feature layers published from ArcMap to the Enterprise Server and automatically registered as items in Portal do not appear in the list of available layers under Search for Layers when attempting to add content to a web map in Portal. If instead of using Search for Layers under the Map Add, I choose Add Layer from Web and provide the REST endpoint URL, it will find the layer and add it to the map. Meanwhile, other items I manually registered from an independent non-federated and unrelated production Server do appear in the list when using Search for Layers under Map Add.
Is this a bug, an annoying feature, or did we do something wrong?