As part of the design process for what ended up becoming GNOME 40 the design team worked on a number of experimental concepts, a few of which were aimed at better support for tablets and other smaller devices. Ever since then, some of us have been thinking about what it would take to fully port GNOME Shell to a phone form factor.

Source: Towards GNOME Shell on mobile - GNOME Shell & Mutter

This is actually pretty impressive for GNOME. I have my doubts that it would ever catch on, but hey, maybe I’ll be surprised and Microsoft will back it.