I would like to see this too.
I use JumpCloud as LDAP server (it does much more, including syncing users with google suite or office365 accounts and enabling SSO to many web apps).
JumpCloud requires an agent installed on machines in order to synchronise local users with the JumpCLoud directory.
The JumpCLoud agent install for Linux fails due to this issue: https://blog.ypertex.com/articles/jumpcloud-on-unsupported-linux/
I could, as a workaround, do my file sharing from a windows VM (or supported linux VM) but then I feel I am defeating the purpose of managing shares in Unraid.
For now I manually replicate users in Unraid (handful of users and get them to enter their password when I create the user!).