I'm using Lubuntu 15.04 15.10as installed from a x64 live desktop iso with 3.19.0-15 4.2 kernel base image

You will need a USB keyboard, a USB hub and a spare USB stick 4GB or more formatted to FAT 32
Use "Startup Disk Creator" to make your USB stick bootable and load your ubuntu ISO

Cube USB seems to fail config on bus powered device if your USB key and keyboard draws over 200mA, to resolve this:

• Use powered hub, or
• Manuall configure USB ie. "echo -n 1 /sys/bus/usb/devices/[usbdevnum]/bConfigurationValue" or
• Hub that does not comply with USB spec may also work as it reports less current than it draws

Use driver for the RTL8723BU from lwfinger on Github ("https://github.com/lwfinger/rtl8723bu") and compile it on a pc that has the same kernel as the lubuntu you are installing.
To compile this you will need Git and build-essential from the repo (sudo apt-get install git build-essential)

• Get the driver ("git clone https://github.com/lwfinger/rtl8723bu.git")
• Compile it (sudo make)
• Copy the compiled 8723bu.ko file to the Cube and put it in /lib/modules/3.19.0-15-generic/kernel/drivers/net/wireless
• Make it root owned (sudo chown root:root 8723bu.ko)
• Run a "depmod -a" to refresh the module list
• Then "modprobe 8723bu" to load the driver and your wifi should come up.

As soon as you have WiFi running, update all your software (sudo apt-get update&& sudo apt-get upgrade)

The PCM sound card is an Intel PCH (Realtek ACL283 chip) but the ALSA driver will default to HDMI, to easily change this:

• For Audacious only: Open Audacious and go into the settings
• Audio - ALSA Output settings
• Select ALC283 Analog (at bottom of list)
• Mixer Device - HDA Intel PCH

To set the sound card (your sound card listing can be found in /proc/asound/cards) system wide create a file called /etc/asound.conf and save to it:

pcm.!default {
type hw
card 1
}

ctl.!default {
type hw
card 1
}

lwfinger on github has a bluetooth driver for the RTL8723BU (USB ID 0bda:b720)

• Use the "new" branch of the RTL8723AU_BT repository ("git clone https://github.com/lwfinger/rtl8723au_bt.git", then "git checkout new")
• Compile (make) and install the driver ("sudo make install")
• Enable the driver on the kernel (modprobe btusb)
• Run the bluetooth manager

Be aware that the keyboard has 2 full size USB ports in it powered by a terminus technology 4 port USB hub (USB ID 1a40:0101)
The touchpad mouse has the left and right mouse buttons embedded underneath the lower right and left had sides of the pad itself.
The touchpad itself has some special features built in, swiping from the left of the pad onto the pad is backspace etc.

Install "onboard" for an onscreen keyboard (sudo apt-get install onboard)
I found that i could not get the on-screen keyboard to work for logging into the cube.