I don’t think there’s anything in a phone that’d stop its core functions in a vacuum. The human trying to use it, not so much.
I was kind of kidding, but I was also kind of intrigued by the idea. My instinct is that it would work in a vacuum, but that is just a gut feeling. But I also could not think of why one could not.
Overheating could be a problem. cooling by thermal radiation alone maybe isn't enough