So based on your experience the new Chromebook Duet 3 no longer supports the original Lenovo USI pen, but now requires a ...

USI 2.0 Stylus Pen [pcworld]

as listed under Duet 3 Tech Specs

However I cannot find an updated "USI 2.0 Stylus Pen" on Lenovo's site.

[EDITED The Penoval USI702 with tail eraser should work as it is listed as compatible with the newish Duet 5. IT DOES NOT WORK]