Is there anything comparable which doesn't require a smartphone? On the laptop and runs Linux?

I don't trust the large closed hardware blobs on my smartphone.

ps: does anything technically prevent berty from being used as an application on a computer?

Well, in fact they have a CLI client ( that I haven't tested ) [1] and their site says they're going to be available also for Mac, Windows and Linux.

https://github.com/berty/berty