This could be a workaround until proper component is done.
Should work with any polyline, open or closed; if radiuses too big > fail.
Not deeply tested, not even tried with a list/tree of polylines.
Maybe it helps…
Edit: if you want different behavior about radiuses input, change RepeatLast/Wrap of circled component…
Try this also; you can select every two curves of every corner and apply fillet, and of course you need always match outputs ; it is not a final solution you need find a way to join the result