I have the Busch & Müller Toplight View tail light connected to the output of the stock Supernova E3. That is working fine. It seems at least some lights of some other brands are able to work with the Supernova output.

I am generally happy with Busch & Müller. The Luxos U 70/90 lux is very good. If I was going to replace the stock supernova on the Birdy, I might go for the IQ-XS 70/80 lux. https://dynamolights.com/busch-and-m...lumotec-iq-xs/