If you have used Linux for a while you will remember the days where Ubuntu was trying to be self sufficient by making their own version of almost everything. The Upstart init system, the Mir display server, and the Unity desktop. One thing that many people miss about the older versions of Ubuntu is the Unity desktop environment. Many people think that it has died, but it is still alive! I am going to get into how it still around.
Lomiri has actually very little to do with the original Unity7 as found in older Ubuntu Desktop releases. It is based on the newer qt based rewrite originally called Unity8, which is a mobile first and gesture based UI.
The idea is that this is a “desktop” primarily useful on touch input devices that are convergent, meaning you can plug in other input devices and a larger screen for example via a docking station and then use it as a regular desktop.
While Plasma Mobile has a similar goal as Lomiri, it is years behind in developmemt and only slowly catching up in terms of usability compared to Ubuntu Touch which uses Lomiri.