Where are all these columns coming from on the Entries in happy-lagger.test project? I just started looking around the example project happy-lager, and I realised that on the Entries there's a bunch of columns displayed that I don't see on my company project (URI, Service Icon and some others in different Entries, such as background colour or image thumbnails). I didn't know this was possible, but it's great. How are those set? 

FYI: Our project was updated from Craft 2, I don't know if this might be related.
On every entry type (or even on the "All entries") you can specify the columns visible in the Panel. Click on the cog at the bottom of the light-grey sidebar. You'll have access to all entry' fields!

The magic of Craft ;)