Based on maximum authorized weight. I would say these vehicles don't have ANY authorized weight, because they're not authorized at all in EU or UK, but Cybertruck specs ask to follow the GVWR [0] of the vehicle, that's right over 4000kg
UK common driving license (cat. B) seems to be similar to other EU licences (Spain here) I guess because previous EU standardization.
"Category B" licenses (post 1997): "You can drive vehicles up to 3,500kg maximum authorised mass (MAM) with up to 8 passenger seats." [1]
0: "When loading cargo, always consider the vehicle's Gross Vehicle Weight Rating (GVWR). The GVWR is the maximum allowable total mass of the vehicle including all passengers, fluids, and cargo." https://www.tesla.com/ownersmanual/cybertruck/en_us/GUID-12A976DD-EB60-431B-AFF1-5A37E95006DB.html
1: https://www.gov.uk/driving-licence-categories