I've installed my own Universal Windows App for all users on a PC, using the DISM tool while being logged-in in Audit Mode.
After doing so, I reboot into OOBE (using sysprep command), create a new user and try to launch this app.
The result is that nothing happens - the app doesn't launch (also checked in Task Manager). In Windows' Event Viewer, I found an entry about AppxDeploymentFailureBlue, which appears there every time I try to launch that app - but it doesn't supply any further information about the problem or its cause. I tried to look for this error code online, but all I could find is some discussions about a corrupted version of the Windows Store app or Windows' built-in apps - which isn't the case here.
Further more, this app has a StartupTask, and its failure to properly launch seems to be blocking other apps from registering themselves in the Startup tasks/apps list (if the app isn't installed, then they are registered successfully).
The solution turned out to be simple in hindsight, but not easy to track down:
Turns out one of the app's dependencies wasn't installed. Seems like installing a Universal App with DISM in Audit Mode (as opposed to when installing as regular local user) doesn't give any indication about missing pre-requisites.
In order to figure out which dependency was missing, I went over the App's AppxManifest.xml's <Dependencies> section. In order to check which are installed and which aren't, I used the following command: Dism /Online /Get-ProvisionedAppxPackages.
After installing the missing package (in my case, that was Microsoft.VCLibs.140.00.UWPDesktop), everything went back to normal.