Can't share anything after Upgrade to 11.3: Permissions don't work

So far, I've been running my FreeNAS as a pure backup server that fetches data automatically from my cloud. In the rare cases that I had to actually access data, I used SSH / WinSCP and the root user. Around 3 weeks ago, I've upgraded to 11.3 (Train STABLE) (from 11.2).

I have a Pool DATAPOOL with two subpools that I would like to share: Crypt via SMB and Test1 via Webdav (or anything else - it's only for testing).

Now I'm trying to get some SMB shares up and running. I can...

Can't share anything after Upgrade to 11.3: Permissions don't work