Kinda. You can set up a matrix server and signal bridge. That's what I am doing with all chat applications.
Hm apparently there is a CLI interface that can be used as well.
True. I think the bridge even uses it behind the scenes. I am only running the bridge because I already have my matrix server with ever IM bridged through to it. It's pretty amazing to be honest.
No, you need an active smartphone and a phone number to sign up to Signal and register the desktop app at the moment. Maybe that'll change once they introduce usernames.
hm, a bit annoying really. Wonder if a KVM + android x86 virtual machine would suffice. Will try it out when I have time...
You need something with a sim so they can call or SMS you.