I have an ASUS Tinkerboard and I have been using Armbian 18.04, but I would like to know if there is a way to install the Ubuntu-Mate desktop? 

I tried the following after a fresh install of Armbian 18.04 and before I did anything else. I did not install any desktop from armbian-config.

sudo apt update

sudo apt install tasksel

sudo apt install ubunutu-mate-desktop

 

And while this looked promising and went through the motions (and it took forever), in the end it did not work. I only had the command prompt. Again I did not run anything from armbian-config yet.

 

Thoughts on how to make this work? I assume it is possible. Thanks.

did you try

startx

to see if it would kick off the desktop mode?

 

I did try startx, it did nothing. Thanks.

Don't know about 18.04, but found this

https://ubuntu-pi-flavour-maker.org/download/

Is in Spanish but maybe with traslantion or see snapshots you can reach the objetive: https://raspberryparatorpes.net/raspbian-2/raspbian-mate-instalar-mate-desktop-sobre-raspbian-lite/

The original work is taken from https://ubuntu-mate.community/t/how-to-install-a-minimal-mate-desktop-on-your-raspberry-pi/16077