Desktop environment starts but graphical installer does not

Basic noob question, used Etcher to zap 23.05.2918 to USB stick.
Server boots and loads desktop environment, then sits there, no graphical installer.
Manual says “can take some time” so waited 30 minutes and nothing.
Is there something I am missing.
Never had this with any distro so ???

Before the desktop appears there is a quick glimpse of the execution:
<<< NixOS Stage 1 >>>
Starting systemd-udevd version 253.6
/dev/loop0: Can’t open blockdev

However moving the install USB and target SSD to another PC and it starts up fine.

A few pointers…?