There are three main categories of entry into a device via zero-days: WhatsApp/Signal, SMS/MMS, and Firefox/Chrome/Safari. If these can be isolated, entering a device could become harder.
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You can do tons of neat things with it. You can also cut off environment variables, cut off the x11 socket, only allow certain dbus channels, etc. You don't need a docker container or anything, Flatpak is a container technology.