I wrote:
I have two systems that were recently upgraded from Fedora 26 to 27 using DNF system-upgrade. Both were successfully running a KDE desktop for several generations previously, including on F26. In both cases, after the upgrade, starting KDE showed the splash screen and then a blank screen with only a pointer cursor. The keyboard and mouse worked but the screen remained blank. Both systems are set to start in systemd's multi-user mode; KDE is started with the startx command.
Prasad K wrote:
I'm guessing some dependent systemd service did not start causing the KDE startup issue. Instead of startx, install a login manager like KDM or SLIM and enable the system to launch GUI at boot and then reboot the system and see if the issue gets resolved.
I tried that with the first system, the one which I have already re-installed, before the reinstall. The result was the same except that killing the hung system was more painful.