Yes there is rapsberry pi (armv7 architecture) download but it will not work on tinkerboard.
The hardware is not the same even if it the same armv7 architecture so it need a different kernel, drivers and bootloader ...
I use already mate over their debian environnement, but I want to make a version of ubuntu mate for tinkerboard and it is what is about this page :
It is for making new ubuntu mate version for another armv7 boards.
But the version available is old (15.04), I am looking for if is it newer build of it !
Then I could do my custom version with tinkerboard specific bootloader, kernel and X11 drivers.
So my question is where I could find newer versions if they exists.
Did you look at my link ?