The world's first Ubuntu phone is just a variant of an existing low-end Android phone, but it's already picked up some carrier support - although perhaps not quite in the way that you were expecting.
Aquaris e4.5 RSS
The first Ubuntu-based phone will go on sale next week - but it's actually an 'Ubuntu Edition' of a low-end Android handset with a 4.5" qHD display, 1GB RAM, 8GB storage and 1.3GHz MediaTek processor.