Can I use my laptop as a second monitor?

Question

linux

If possible, how? On both Ubuntu 16 devices.

Answer 1

Not a trivial solution to the problem.
1) Buy an external capture card (many pretend to be a monitor).
2) Connect the card to the laptop
3) HDMI connect the PC to the card
4) Start broadcasting the picture

Answer 2

Not quite right, but you can do it like this: Synergy (if you search, there are officially free assemblies ... although even paid space is not worth it).