The first issue I ran into with Kubuntu 15.10 was very early in the process. Booting from a flash drive would take me to the bootloader (Unetbootin), allow me to select the "Start Kubuntu" option, flash the Kubuntu logo for a fw minutes, and finally drop back to a busybox prompt saying it was not able to find a live filesystem.
My motherboard isn't exotic, my USB controllers are Intel 9 series, which have been well supported for a very long time. Of course, moving to different ports, trying both USB2 and USB3 ports, etc were all tried.
With a little debugging (use the `dmesg` command to see the kernel's log), it showed that the USB controller was trying to reset my usb stick for some reason, and it was failing. This caused the kernel to generally not recognize that the stick existed.
The "fix" I came up with was:
. Reboot to the Unetbootin boot menu
. Scroll to the Start Kubuntu option
. Hit Tab to edit the boot options
. Remove 'quiet" and "splash" options
. Hit Enter to boot
. Wait for kernel messages about resetting the USB controller
. Unplug USB stick, plug into a different port
. Installer find the stick, the installer finishes loading.
If you're having the same issue, hopefully this helps you get another step farther in the process!