It does, it's called FreeIPA (or RedHat IdM). The only GPO parts it doesn't do are those that are not related to policy in the IAM sense (i.e. configuring some application related thing). There's other systems for that, just like on Windows you practically never run GPO without anything else. On top of that, you can pay RedHat or Canonical to host it all for you on any cloud or non-cloud.