Several years ago US-based Reviver Auto developed E Ink based car plates, called the RPlate pro, that can show customized messages when the car is parked, and also can update plates without delay. In 2018, several states in the US started testing the digital plates.
Towards the end of September 2022, California issued a new law, AB 984, which makes E Ink displays a legal alternative to standard metal plates. There are some conditions to the use of the display. The only company that got approved to is indeed Reviver Auto.