You do without memory cards
Memory cards cannot be reliably encrypted on all devices. It is also possible to restore data that was saved on them when they were previously used with other devices. Therefore, only use memory cards if you know what is stored on them and if you have overwritten them beforehand.
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Some older Android devices also create a signature of apps used on your memory card by creating separate folders for apps used. This allows conclusions to be drawn about the apps you are using. Caution! Overwriting flash memory is often not 100% possible. Data can still be left behind.