In order to Install Ubuntu on your system, please follow the tutorial available from the UP Wiki.

Ubuntu versions currently validated on UP series (Not for UP Xtreme):
Ubuntu 16.04 LTS (Kernel 4.15)
Ubuntu 18.04 LTS (Kernel 4.15)

Ubuntu versions currently validated on UP Xtreme:
Ubuntu 18.04 LTS (Kernel 5.0)