Muon package manager is an alternative GUI for installing and updating updating packages.
Useage
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To update your packages press the gear button with a clockwise pointed arrow. If updates are available press the upward pointing arrow with a dot on top to install the updates.
Version
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Lubuntu ships with version 4:5.8.0 of muon package manager
How to Launch
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To launch muon package manager from the menu -> System Tools -> Muon package manager.