Hi.
Please see here: Privacy comparison PlayStore vs APK Store vs F-Droid version
The Android App licence (and the iOS App licence) and the Desktop App Supporter Certificate are different things. The app licences (one for each Mobile-OS) enable you to use the apps that are provided by cryptomator. The Desktop version can be used without buying a licence. However if you want to have the darkmode theme, your support is requested by either fund the development or contribute to it e.g. by translating, implementing features, influencing or other activities. See here: Details for the Supporter Certificate.