Unable to boot to desktop, after installing Ubuntu 19.10.1 on Raspberry Pi 4 and installing kubuntu-desktop

I'm glad to see that someone else has experienced EXACTLY the same problem that I have! And here's the work-around I found--not a solution, but it gets Kubuntu working. When you get to the point where the system hangs, you can switch to another TTY. I believe the system starts in TTY1, which is supposed to be the one used for the graphical interface. You can switch to TTY2 by pressing CTL+ALT+F2, and you should get a login prompt. Login as Ubuntu, and when you get a prompt, execute "startx". This will bring up the Kubuntu desktop, and you are already logged into it. And I have to do this each time I boot up the system. I think this must be a bug in the Kubuntu installation routine, but I have yet to find a way around it. Sure would be nice if someone fixed it. There ought to be a file somewhere that you could insert the "startx" command and have it run at bootup, but I don't know enough about Ubuntu to do it.

I just installed the latest 20.04 version and this exact same issue happened with Kubuntu and Lubuntu. Removing cloud-init does not solve the issue. Switching to TTY2 by pressing CTL+ALT+F2 does work and allows running startx.

However, the solution you probably are looking for is adding the following to /boot/firmware/syscfg.txt (or usercfg.txt):

dtoverlay=vc4-fkms-v3d

This loads the "fake" KMS framebuffer which improves desktop usage and fixes the boot sequence so it goes directly to desktop. Incidentally, this worked but it caused my 1080p display to underscan, which I fixed by adding an entry in syscfg.txt as follows:

disable_overscan=1