Kiosk desktop application updates

Hello, I am developing a Unity game as simple kiosk application. I was looking for possibility to implement updates and I discovered snaps. I was reading that snaps are updates automatically and this is nice but not in my case. End user will be power on machine only for using application. There will no be time when machine will be power on and application will be closed for update. Next I discovered Snapd Rest API and wanted to write simple updater application but Refresh action require authentication. User cannot provide any credentials it should happens automatically. I can changing anything in system because application will be distributed with system.

Could someone give some tips how to bite this topic? How having desktop application running all the time preparing updates?