Currently there is an issue specific to the following environment combination where graphics do not render correctly:

The combination is as follows:

Virtual Machine (does not matter which — qemu/libvirt/vmware,virtualbox,etc)
+
X11
+
KDE

The KDE live ISO will not currently load inside a VM due to the following bug:

https://gitlab.freedesktop.org/mesa/mesa/-/issues/6923

> This issue does not affect hardware installations with dedicated or integrated GPUs and a head/display attached.
> This issue does not affect GNOME inside a VM
> This issue does not affect Wayland sessions, however the liveCD session starts in X11 so a workaround is required:

Workaround:

Send Ctrl+Alt+F3 to the VM to drop to tty
Login as root
run the following commands:

cd /usr/bin
mv startplasma-x11 startplasma-x11.bak
cp startplasma-wayland startplasma-x11
systemctl restart sddm

This tricks the live session into reloading with wayland instead of X11. This should then allow the graphics to load properly so that you can run the installer within the VM.

Note: After installation you’ll need to make sure to login using Plasma (wayland) from the sddm drop down. This is usually the default after installation.