This thread is not related to Assistive Technology, since you're talking about different methods of communication, such as a video relay service.
Can you find out who's their VRS provider?
Sorenson provides a VP200 for deaf, but if your friend does not have a TV, your friend needs to get a TV tuner that is compatible with Linux (stay away from AverMedia AverTV ATSC H788 -- it doesn't work with Linux). This is quite complicated, so if your friend is not using Sorenson VRS, there should be video chatting applications that might work with other VRS services.
Make sure your friend gets a webcam that is compatible with Linux.
I don't know of any VRS services, such as CSDVRS, ViableVRS, etc. that work with instant messaging applications that includes support for webcam.