You do that inside the SVG. Instead of having a yet another path or a group of paths, you just have that `use` element (which just references some other node).
Basically, it lets you reuse something, but you can transform it and set some styles.
We consider the system font critical, and we render the page with that because it it will load instantly. The custom font is then loaded after the content and used on the following page.
Note: this setup is only used sparingly on our site as it has been waiting for this piece of work to be completed.
Curious, the first time I read your post, I saw exactly what I described, which is all text was missing for a second, and then appeared in the custom font.
But when I try now, I get the system font for a second, then it switches over to the custom font.