evenwichtLenovo USB-C PSU for laptops powers a Rasberry Pi, but cannot simply charge bicycle lights. WTF?
The lights most likely do not have the extra circuitry to talk to the charger to negotiate voltages. Since it’s a charger that can change voltage as you stated then the device must be able to say “hey give me 5v”. You will need to use a dumber 5v only charger for those devices.
What would be the meaning of a default voltage then? My understanding of USB PD is that 5v is a default, which I took to mean it would deliver 5v in the absence of a handshake.