https://api.jqueryui.com/sortable/#option-helper

Function: A function that will return a DOMElement to use while dragging. The function receives the event and the element being sorted.

Does this function actually want a native JS Element or a JQuery<HTMLElement> returned?

and the element being sorted.

This means the 2nd argument is JQuery<HTMLElement> or a native JS Element ?

Thanks for clarifying this, ideally it would also be updated in the docs page
(I can PR an update in the TS @types once it's clear)