Lubuntu is a lightweight Ubuntu distribution for older PCs.
With the latest 18.10 release that has LXQt desktop, it makes it easy to change the location of personal files and folders.
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Here is how :
From the start menu, go to Preferences > LXQt settings
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Next, click on LXQt Configuration Center.
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Then select Session Settings.
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Over here, from the User Directories section, change the default location where various personal files are stored like Desktop, Downloads, Documents, Music and so on.
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Click on the folder icon to point the default directory path to a new one.
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Click Choose. Log out for the changes to take effect.
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The new location should now be the default after logging back in.
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All done.