Microsoft has released Windows 10 Insider Preview Build 10158 for PCs today. If you are Insider and have upgraded to build 10158 then you’ll find that the Insider Hub is no longer available. This is because the Insider Hub is no longer pre-installed starting with this build. If you want to re-install it, please follow the following steps:
Go to Settings > System > Apps & Features ,
Click on Manage optional features (as shown in the pic) and then Add a feature
You’ll get a list which is in Alphabetical order, select the Insider Hub entry and click Install.
And the app will be installed.
But when I installed it, it was no where got listed either in All apps as New or the Insider Hub app tile shown on Start. So I clicked on ‘Search the web and Windows’ (besides Start Window flag) and just entered Insider Hub and it was listed as Trusted Windows Store app. So I right clicked and pin to taskbar as well as Pinned to Start. And its now working.