Could be, but I didn't saw anyone mentioning it. Did you?
Or they will add external signer support with a future update.
Discussion
I just started with the citadel dispatch episode. Maybe it is mentioned. They are mentioning that this is still alpha and can / will be improved in many ways.
I think they will support amber in the future. But I'm curious what they say on the pod. Maybe you can tell after you've finished listening?