What's the appropriate method of dealing them? Could I just remove them?
Probably - but where are you seeing these "Account Unknown"? are they
on Permission lists for objects such as files and folders - in which
case you probably can remove them.

In the Security tag of the file/folder's properties.

I guess I could delete them.

But what if this "Account Unknown" owns a folder?

Also your use of Xubuntu appears to have damaged your keyboard as the
product name is Vista with an "s" not a "$"

It's another PC (home server), not the workstation where I finish most
of my personal tasks, including games of course.

--
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