Ok. I can only recommend this (if you didn't do it before):
Go here:
https://github.com/celeron55/minetestScroll down and follow the instructions for Linux by copying them and pasting them in your terminal (I don't know how much you know about Linux, but start with
SUDO apt-get install build-essential libirrlicht-dev etc. etc.
You can try minetest now or, if you want alwayscraft, try to install that one now (after installing the regular minetest)
P.s. If you already did this, or if it doesn't work, sorry for the trouble. Maybe then you should try to install Lubuntu and try again...