Is it possible to use a laptop with thunderbolt 3 as external monitor? Considering an external gpu can be used, can an 'internal' gpu be used too?

Question

I'm looking into buying a new laptop and a lot of laptops I'm looking at have one or more thunderbolt 3 connections. Suddenly I had a thought. External gpus are more and more common nowadays. And I was wondering if it's possible to connect a normal internal gpu inside a desktop to a laptop using a thunderbolt 3 port and use the laptop as external monitor?

I don't know how the connection between e-gpu and laptop works, but one way or another it should spit out a raw video signal and return that to the laptop. Isn't that exactly the same as a normal internal gpu?

Answer 1

The commercial app Synergy lets you run one app across two PCs with one keyboard and mouse, as do Open Source alternatives.