The samba project (samba.org) offers a compatible implementation of the active directory network protocols that Windows clients happily use as an AD server.

Not sur if it helps and serves your needs, but we have created a samba-container project ttps://github.com/samba-in-kubernetes/samba-container/ that also features an active directory server container.

pre-built images are available here: https://quay.io/repository/samba.org/samba-ad-server

sure, this is not native Windows AD, but should be compatible enough for most purposes.