To be clear, you do NOT delete the whole WindowsApp folder. For this game, the launcher is directly inside the folder in a folder that includes "oxyna" in its name. The actual data downloaded should be in Mutable in a folder with the same name.
This is what worked for me. Thank you so much. So to recapitulate:
- You need to set your Explorer to show hidden folders&files.
- You need to change ownership of WindowsApp folder to yourself (remember to checkbox the option that makes it apply to subfolders).
- You need to delete the "oxyna" folder and also everything inside the MutableBackup folder (don't delete the folder itself).
Microsoft Store sucks so much. How could they make this game installation so bad? It installs stuff on 5 different places on your PC (including settings on MyDocuments) and only deletes one of them upon uninstall (10 GB out of 70). Steam and other game/app stores do something similar, but by far not at this level. This is such an embarrassment.