With useSingleton() className cannot be set

[miracle2k]

See this example:

https://codesandbox.io/s/modest-fire-bfun4?file=/src/App.js

I can see that in the issue history there was work on this (e.g #129) but I think it might have been lost.

[atomiks]

If you need a temp fix

<Tippy
  onCreate={instance => {
    instance.popper.firstElementChild.classList.add('...');
  }}
/>