I’d check the setting you have for that menubar icon in bartender. There may be a conflict that is causing it to revert when bartender hides the icon. Set the icon to always visible or never visible and see if that changes the behavior of the setting.
The solution to keep is in the Menu Bar was to adjust this setting in System Preferences
So that half of the mystery is solved.
But the icon continues to randomly change. When it has a vertical line denoting the display split into two, it means Universal Control is working. When the vertical line disappears in the menu bar, Universal Control is not working.
The mystery remains as to why UC only works intermittently.
What is the physical configuration of your devices and could there be anything interfering with the ad hoc connection the devices are trying to negotiate?
Count me as another user where Universal Control works only intermittently, no apparent rhyme or reason for why it works sometimes and not others.
I’ve done a little digging and concluded that Universal Control’s flakiness is caused by physics.
As we know there are infinite universes, but due to the conflicting multitasking models used by iPadOS and macOS, universal control can only work in one at a time.
So, sometimes, UC works in the universe I’m in, and other times it doesn’t because it is busy working in one of the other infinite universes.
Or it’s buggy.
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