I've got Process Monitor running and it shows that it has to read:
HKEY_CLASSES_ROOT\Local Settings\Software\Microsoft\Windows\CurrentVersion\AppModel\PackageRepository\Packages
Under that key you will find a long list of long numbers which apparently correspond to the different apps. If you right click on the above key and select Permissions, then System and Administrator should both have Full Control. Do they? Click on Advanced and verify that the Owner is System.
Try a few of the sub keys and verify that they look the same.
I expect that will be OK since it does list the apps but just want to be sure.
The info that is missing appears to be about the files themselves. It reads:
C:\ProgramData\Microsoft\Windows\AppRepository\StateRepository-Machine.srd-shm
But Windows won't let me see the file. I can get to C:\ProgramData\Microsoft\Windows\AppRepository\ then I have to right click and select Properties, Security, Advanced, continue and I see that only Trusted Installer has Full Control. System has only Modify the folder but Full Control of Subfolders and Files. These days the only way to change it is to activate the Administrator Login and then while logged in as the Administrator you can take Ownership and it will usually allow it.
We then read HKEY_CLASSES_ROOT\Local Settings\Software\Microsoft\Windows\CurrentVersion\AppModel\PackageRepository\Packages and the subkey for Photos as an example \Microsoft.Windows.Photos_2018.18091.17210.0_neutral_~_8wekyb3d8bbwe which also has Full Control for System and Admin. This refers us to the file location. For Photos it is:
C:\Program Files\WindowsApps\Microsoft.Windows.Photos_2018.18091.17210.0_neutral_~_8wekyb3d8bbwe (I think you will have a different number at the end)
Unfortunately Windows stops me at:
C:\Program Files\WindowsApps where I have to do the Properties, Security, Advanced, continue and I see that only Trusted Installer and System have Full Control (Administrator supposedly can list files but that doesn't work). Windows says it can't display owner. I presume it has to read this folder in order to get the date and file size. Again I suppose activating Administrator and taking ownership will work but I haven't tried it yet.
I'll try taking ownership from the Administrator login later. Wanted to post this first.