Its model uses the Controller whose input devices are used, and the Target, being controlled by them. Universal Control is responsible for managing connections and routing input and control events to the Target.
handoff
Until these bugs are fixed, versions in iCloud simply can’t be trusted. And mixing them with Handoff becomes even more confusing.
Not back to the Bluetooth purgatory of El Capitan, but still some worrying moments when your trackpad goes missing.
The Eclectic Light Company 