https://snapcraft.io/docs/snap-store-metrics
> the store assigns an anonymous identifier, the device-serial, to every new snapd client it sees. This exchange usually happens when a new installation contacts the store, and the identifier persists for the lifespan of the machine.
> Systems running snapd will periodically make a refresh request to the store, checking the for the most recent release of each installed snap. At that moment, they inform the store of their device-serial along with a list of the currently installed snaps.