I have a problem, installing the High Sierra beta on a Mac mini (Mid 2010) w/8 GB memory and 2 internal HDDs when it detects that Server software is on the disk.
Install to the 2nd non-system disk worked without problem. However, installing onthe system disk that contains Server generates the following message:
macOS 10.13 Beta supports macOS Server version 5.2. To upgrade your Server you will first need to install OS X 10.10 or 10.11 and OS X Server 4 or 5.
The disk is greyed out as a target. The other disk is not greyed out and now has a copy of macOS 10.13 on it. I can boot from either disk and there are not obvious problems of errors.
The Server software is Server 5.3.1 (16S4128) and the OS is MacOS Sierra 10.12.6 Beta (16G12b).
Is there a work around? It looks from this one situation like it doesn't support updating a current server platform but a clean install allows you to install the Beta Server software.