Good question. For me, I’m almost always a mouser, and unfortunately that often means I need to make a conscious effort to even begin considering keyboard use.
TBH I’ve never thought of “drag drop” as being a keyboard thing. That is, more of an “enhancement” for those that could, while (hopefully) not being essential for those that couldn’t.
But I think drag-drop could be approximated using some kind of JavaScript select - move type of code.
Of course that would likely be non-trivial and not “native HTML5” eg.