I have tried putting Ubuntu-Mate on a NOOBS microSD but cannot get it to actually install and run Ubuntu-Mate. Got the file UbuntuMate.zip from https://ubuntu-mate.org/download/. When opened it has a directory \os\UbuntuMATE with what appear to be the appropriate files. I have copied the subdirectory UbuntuMate into the NOOBS os directory and then put the NOOBS SD into my RPi3. It allows me to select UbuntuMate for installation, but on launching it hags up with a multi-color square in the upper right corner of my monitor. I let is sit all night once just to see if it was slow in loading the first time, but no luck.
The other Paspberry NOOBS options load correctly and I got Ubuntu running by writing the image file directly to a microSD card.
Any suggestions?