With this Git commit today there is mainline Coreboot support for the Gizmo/Gizmosphere AMD development board. This development board features an AMD G-Series embedded APU and is similar in nature to the many low-cost ARM development boards.
The Gizmo board consumes less than 10 Watts of power, has an open PCB and lots of expansion/development opportunities with the Gizmo Explorer Kit, and could be nice for hobbyists or those wishing to prototype new AMD x86 embedded systems.
More details on the AMD Gizmo x86 development board can be found via Gizmosphere.org. Previously they used SageBIOS on the board, which is a commercial distribution of Coreboot, but now there's the mainline support. The mainlining was done by Sage Electronics and adding in this AMD Family 14 motherboard required 5,000 new lines of Coreboot support code.