Place the ^^ inside the square brackets.

So: Text¹

Text[^1^](https://lemmy.ml)

This will show up nicely in the browser. However, it will not show up correctly in Jerboa.

In Jerboa, this will show up correctly:

Text¹

Text<sup>[1](https://lemmy.ml)</sup>

But not in the browser.

Not sure of a way that works for both.