MirrorHall creates virtual second monitors over the network using UDP video streaming among Linux desktop or mobile devices. It is optimized for low latency, and is based on gstreamer and GNOME's mutter screen sharing APIs. This is an early proof of concept and has several drawbacks. It is nowhere near usable at production level, and the video stream is not encrypted over the network. Proceed at your own risk. This app supports hardware encoding for some ARM and x86 devices, more specifically:

Modern Intel and AMD CPUs (vaapi) Qualcomm CPUs (via v4l2)

If you have an unsupported CPU/GPU configuration, a software fallback will be used at the expense of some performance and CPU load.