I was trying to install bottles when it gave me an error message:
error: Failed to install org.gnome.Platform: Flatpak system operation Deploy not allowed for user
How do I fix it!?!?!?
Crostini Bottles Error
It seems to me that your user lacks the permissions to install apps to the system installation. These permissions are handled by Polkit and configured with their format.
Maybe your system doesnt allow a non-administrator to install apps on the system installation. Maybe the configuration is missing or bad configured.
In my view this is best discussed with your IT administrator (if applicable) or your distribution.
As a short-term workaround you could append --user to flatpak install. This will install the apps to a local installation in your user directory.