Maybe you are looking for Web Site Hit Counter?
I don't know if that's even possible to have it for just opening the HUB but not opening the apps.
For Apps maybe you can use HTML code to embed it into Qlik Sense and use it in front end to show how many number of users logged in that app. The counter will just give you number but not detail.
Maybe dig more into how to do Mashups and you can use that counter?