You don’t need a licence if they are in the category of electric bike, meaning they cannot be self propelled (you need to peddle) and they have a limiter limiting the speed to 25 km/h.

Unfortunately, these things are wicked easy to circumvent. Many retailers will sell you a throttle (meant for moving the bike while walking with it) and changing the speed limiter and peddle requirement is as easy as going into the software settings. This results into what is effectively an electric moped without the licence plate and requirement. According to the law, such a vehicle requires you have a license and wear a helmet, but of course nobody does.