This was the best hint in the whole thread here. Great job for pointing on that solution. I suggest trying this fix because that worked immediately for me. The other hints do simply not work because something within the app folder is messed up. Also the
other fixes do not remove the whole folder so the broken files / folders are left there. However I will now write down a detailed description and the steps I did to fix the issue:
1.) Download https://docs.microsoft.com/en-us/sysinternals/downloads/psexec
2.) Extract the archive to e.g. d:\tools or any folder you want (but be aware that you have to change the command in step 4.2)
3.) Open an elevated powershell (as administrator) - right click on windows startmenu logo - Windows PowerShell (Administrator)
4.1) run this cmd: Get-AppxPackage Microsoft.Windows.Photos | Remove-AppxPackage
4.2) run this cmd: d:\tools\PsExec.exe -sid c:\windows\system32\cmd.exe
5.) a new command window will open - check if the path in step 7 exists (the actual folder of Windows Photos App)
6.) close everything except the new command window opened in step 4.2
7.) run this cmd: rd /s "C:\Program Files\WindowsApps\Microsoft.Windows.Photos_2018.18051.17710.0_x64__8wekyb3d8bbwe"
8.) hit "y" or "j" to confirm
9.) check if everything got deleted, if an error occured check if you closed everything except your command window and start over with step 7, maybe a restart is necessary here before starting over with step 4.2
10.) Reinstall Photo App from Windows Store, voila!
Credits go to winhelponline and Rovern
https://www.winhelponline.com/blog/photos-store-apps-file-system-error-2147219196/