The Thule EasyFit Carrier XL is an extra long bracket for mounting to rear bicycle racks with at least 25kg capacity. You can then easily mount a Thule EasyFit seat and most bicycle panniers. Additional brackets allows you to change the seat from one bicycle to another. You will need an e-bike adaptor to use with electric bicycles with the battery in the rear rack.
Thule Yepp Maxi EasyFit Carrier XL Instructions