Okay, I have received the following answer from support:
According to Lenovo's Smartfind, only the Precision Pen 2 is compatible with the IdeaPad Duet 5:
https://smartfind.lenovo.com/accessorie...

Since the Digital Pen 2 is not mentioned, it is not meant for this computer.

Here is the link to the compatible pen:
Lenovo 4X81H95637

Hello! This pen works for me with an i7 Lenovo IdeaPad Flex 5 16IAU7 product number 82R8002HMZ.

Sorry, I'm not sure. Looking at the photos, it looks like it is, but the best thing is to contact digitec's service department to be sure.
Have a nice sunday