I'm specifically interested in making the case of books specifying "font-variant: small-caps" work. At the moment the Kobo kepub reader fakes these small caps instead of using true small caps, even if the current font supports them. Based on my experiments and reading the CSS specs I haven't found a way to do this, hence my question.
The only way I can currently think of that might work is to side-load a "small caps only" font like
Vollkorn SC and change all places where books specify the font variant to also specify the different font. However this would require modifying each book individually and is thus not feasible, so I haven't tried if this would even work.
Since jackie_w mentioned that Kobos can actually display true small caps I'm now curious if it's possible to do this in a general way that wouldn't require me spending weeks on modifying all books individually.