> Those are all apps running in the cloud.

Authentik and others can be deployed as docker containers that can be deployed any way you wish.

> I meant the classic Windows AD company LAN like solutions where the clients, server and network are tightly coupled.

In any mixed environment these days of Windows PCs, MacOS, and Linux, yeah, you can use a SaaS like jumpcloud with support for all of them, or you can integrate them into the ldap/kerb backend of your choice. Bonus points if your network devices are using RADIUS auth to the same identity source.