I think that my quest for a free Linux and Windows word processor that can create smart quotes, sometimes called curly quotes, has come to an end, and I can concentrate on my writing again because like other writers I would rather be writing a novel than searching for software.
Firstly, why bother with smart quotes?
Why not just use the ‘couple of upright ticks’ that most word processors and text editors provide?

One argument is that smart quotes ‘look prettier’ than a couple of upright ticks. I can understand this, let’s face it a couple of ticks does look rather computer generated. Smart quotes are computer generated too, of course, but they just don’t look quite as computer generated.

The reason why I decided to look for a word processor that could create smart quotes was, I downloaded a few novels from the internet and noticed that they had smart quotes.
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That was it! I was in love! Smart quotes are my kind of girl.
Anyway, here are the word processors that I’ve used to create smart quotes so far: Libre, aka Apache, Abiword, and Focus Writer.
The bad news is (or maybe it’s just me,) they all have problems creating smart quotes.
Libre/Apache will create them, but only after you’ve worked your way through what feels like a million menus and sub menus. ~And even then I have problems with it.
Focus Writer will also create them but that blank screen that tells you you’d better get focussed on your writing or else is too challenging for me. In fact I find it quite dictatorial. “Ve haf vays of making you focussed.”
Abiword is probably the easiest way of creating smart quotes, but even then they tend to be the wrong way around. For example, it can create closing quotes (the ones at the end of the word or sentence) when you want opening quotes, and vice versa.
In my experience it’s difficult to create smart quotes aka curly quotes successfully, and it’s better to avoid using them if you can do.