I think there's some confusion in terminology. The OP seems to be using "link" to mean use elements with external references. Other people are interpreting it as the use element in general, or as hyperlinks.

Inkscape supports the use element with references to internally defined elements.

Firefox supports the use element with references to externally defined elements.

Inkscape has a fairly basic interface for creating hyperlinks from elements. It doesn't provide any mechanism for following them.

Firefox supports following such hyperlinks the same way it does HTML hyperlinks.