Linux virtual machine's window disappears at the initial launch after installation, and the 'You are running Coherence view mode' notification appears in the middle of the screen.
Coherence mode turned on.
Parallels Desktop supports Coherence view mode only for Ubuntu virtual machines.
NOTE: Coherence mode is not supported on Linux machines based on GNOME (Fedora/Centos/RHEL), KDE (Kubuntu) and different custom Linux graphical interface.
Coherence is a view mode that allows you to run Linux applications on your Mac, just like they were native Mac applications.
To exit Coherence view mode, click on the Parallels icon at the top of the screen > View > Exit Coherence.