The best way to go around is :
- install solaris 11 with the text installer. make sure you install solaris without the gui.
- when solaris has been installed, go on the console, and manually install the desktop environment, like so:
	Code:
	root@geeklab:~# pkg info -r solaris-desktop
          Name: group/system/solaris-desktop
       Summary: Oracle Solaris Desktop
   Description: Provides an Oracle Solaris desktop environment
      Category: Meta Packages/Group Packages
         State: Not installed
     Publisher: solaris
       Version: 0.5.11
 Build Release: 5.11
        Branch: 0.175.1.0.0.24.3
Packaging Date: September 19, 2012 06:53:17 PM
          Size: 5.46 kB
          FMRI: pkg://solaris/group/system/[email protected],5.11-0.175.1.0.0.24.3:20120919T185317Z
 then
	Code:
	root@geeklab:~# pkg install solaris-desktop
           Packages to install: 369
       Create boot environment:  No
Create backup boot environment: Yes
            Services to change:  14
........
 voila ! worked with me on Parallels Desktop 15 on MacOS Catalina - Solaris 11.4 standard installation DVD (USB)
The only thing what is missing are the Parallels Tools for Solaris. Missing Coherence and so on.