There's nothing in the menu bar (is that what you mean? - I don't think Calibre ever shows up there) and the dock icon doesn't show the dot that indicates an app is running (and either clicking or right-clicking on it brings up the menu you'd expect for an app that isn't running). Also, nothing in Activity Monitor, or Expose View.
In case it's relevant (and I should have said earlier), I'm running Catalina on a 2020 Macbook Air.
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