Unfortunately it seems to be a completely proprietary kernel. I did find a paper on it (presented by Huawei in a conference): https://www.usenix.org/conference/osdi24/presentation/chen-haibo

The first line of the abstract reads

This paper presents the design and implementation of HongMeng kernel (HM), a commercialized general-purpose microkernel that preserves most of the virtues of microkernels while addressing the above challenges.

Another interesting tidbit from the paper:

We started the HongMeng kernel (HM) project over 7 years ago to re-examine and retrofit the microkernel into a general OS kernel for emerging scenarios. To be practical for production deployment, HM achieves full Linux API/ABI compatibility and is capable of reusing the Linux applications and driver ecosystems such that it can run complex frameworks like AOSP [42] and OpenHarmony [35] with rich peripherals.