This is available out-of-the-box in Odoo 16.0. The UoM field is not visible by default. Open one of the Products and make the UoM field visible in the "Purchase" tab like so.

There is a possibility to add it through studio's 

if you go into to studio's at the product form. Then go to the vendor section and click on the edit list view on the list of vendors. You can add an many2one or a selection to indicate the What kind of UOM you want per vender.

i dont know if this answers your question but i hope it helped!