Canonical continues to invest in Mir as a Wayland synthesizer and set of platform abstraction interfaces to make it easier for IoT and other "smart" devices to run on Ubuntu Core. Recently, Mir developers have been working on refactoring parts of the graphics platform handling to better handle multiple GPU/display devices.
Mir has refactored its graphics platform processing to better support multiple graphics platform targets/backends working simultaneously, and breaks the logic that display output and graphics rendering are done on the same device/GPU.
This ongoing redesign allows support for hybrid graphics platforms, where the GPU will do faster 3D rendering while display scan output is handled by the integrated graphics card or other device. Mir's redesign is also important for use cases like rendering and output via a USB-connected DisplayLink adapter or similar device.
Mir's Canonical developers, in turn, hope to support hybrid graphics in the next version, which is better late than never.
For more details about the Mir graphics platform, visit UbuntuDiscourse:
https://discourse.ubuntu.com/t/reworking-mir-graphics-platform-apis/39665