Ask HN: An Active Directory for my private life?

Like many here I am sure, I have quite a few digital devices, computers, tablets, phones and so on, running different operating systems. In the old days I was a Windows only guy and had my own PDC running at home,and it worked well, but now I would prefer something cloud based. (I can self-host if I need to). I am looking into self-hosted Samba and that might be as good as it gets, but I was wondering if anyone is aware of a better / different solution? The minimum criteria is to be able to centrally manage user accounts on Windows, Mac and Linux and that they service is available 24/7 via the net. And of course, I am looking for something cheap.