They currently have CBL-Mariner Linux.

They used to maintain [SONiC](https://en.wikipedia.org/wiki/SONiC_(operating_system)) another Microsoft Linux, but last year gave control over that to the Linux Foundation.

They used an still have limited *NIX compatibility since the days of NT when POSIX compatibility was a requirement to win government contracts and Windows Subsystem for Linux is a modern revived and expanded version of that old feature.