It's popular enough that Microsoft and Red Hat target it to produce a single image that will work on all ARM server SoC vendors e.g. Ampere, HXT, Marvell, Qualcomm.
Despite the 'server' in the name it can be applied to any 64-bit ARM SoC. There is also Server Base Boot Requirements (SBBR) that describes the boot requirements for SBSA.
[1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc....
[2] https://en.wikipedia.org/wiki/Server_Base_System_Architectur...
https://genode.org/ has it up front:
We understand the complexity of code and policy as the most fundamental security problem shared by modern general-purpose operating systems. Because of high functional demands and dynamic workloads, however, this complexity cannot be avoided. But it can be organized. Genode is a novel OS architecture that is able to master complexity by applying a strict organizational structure to all software components including device drivers, system services, and applications. The Genode OS framework is an open-source tool kit for building highly secure component-based operating systems. It scales from embedded devices to dynamic general-purpose computing.
keywords: capability-based security, microkernel, principle of least authority, sandboxing, virtualization