At work I joined our Ubuntu server to AD but it is not acting as an AD server but more like a workstation for user auth for Nextcloud. I have not used centrify express. Its been a minute since I set it up so I dont remember the exact details but I set up samba and winbind and in my smb.conf are winbind entries which are whats needed to get it connected.
Heres an older tutorial https://help.ubuntu.com/community/ActiveDirectoryWinbindHowto
I can share my config if you need.
EDIT: Heres a much newer tut that I think is probably better.
The downside to linux is its so stable its "set and forget". I did this once and would probably have to re-learn everything I did over again because its been a year since I did it. Well that, and I'm still very much a scrub to linux. Also for reference I am using Ubuntu 16.04 LTS and Server 2012 R2. I remember it being a pain in the ass to get working but it has since been great.