Ubuntu Mate is an overkill for running openHAB etc.
I’m not sure why your reseller is going to send you a copy, all the info and download links are on the Odroid wiki page
https://wiki.odroid.com/odroid-n2/odroid-n2
(Read it all before you do anything, don’t rush)
Unless you intend to use the desktop environment, I would recommend a “headless” system.
This just uses a command line environment, which is fairly easy to get your head around as most of the time you’ll be accessing the machine from a a bigger computer anyway.
WinSCP / FileZilla etc.
(You might want to add a Samba server to DietPi and setup folder shares, if you want to access the N2 like a network connected device, easy to do, but please search for instructions, there are plenty.
)
I would recommend you download an OS image and flash it onto the eMMC.
Check out www.DietPi.com , it’s very easy to deploy.
There are plenty of others to choose from, I just find DietPi to be really straightforward.
(I assume you have the eMMC to SD or USB adapter?)
Follow these instructions if you’re unsure how to “flash an image to an eMMC”
Once you’ve flashed the OS image to the eMMC, put the eMMC into the N2.
Connect a keyboard and monitor, add an ethernet cable and power it up.
On first boot, the OS will unpack itself and expand to use all of the eMMC card.
Login is
root
Password is dietpi
It will prompt you to change the password, my advice would be not to until you’re really comfortable with what you’re doing, as there is no way to get access if you forget the new password.
(Do change it when you’re happy)
Run these commands
dietpi-update
Follow the on screen instructions.
dietpi-software
Look for “search software” and look for Java
Add a star (press Space bar) to Java
Go back to the main menu and choose “install”
When that’s finished, choose “exit”
Back at the command prompt, follow the instructions from this webpage to install openHAB (stable) for a DEB / Debian
“Apt based system”.
Which basically is a few lines
You’ll have to type these in, unless you suddenly decide that you’re happier to use something like puTTY or a MAC / Windows / Linux command line on your main computer and can then use cut & paste. (Paste in a terminal is either a right click / shift & insert / from the window menu)
curl -fsSL "https://openhab.jfrog.io/artifactory/api/gpg/key/public" | gpg --dearmor > openhab.gpg
sudo mkdir /usr/share/keyrings
sudo mv openhab.gpg /usr/share/keyrings
sudo chmod u=rw,g=r,o=r /usr/share/keyrings/openhab.gpg
Once you have added the above, you’re ready to install openHAB
This line will tell the computer that you want to use the stable version
echo 'deb [signed-by=/usr/share/keyrings/openhab.gpg] https://openhab.jfrog.io/artifactory/openhab-linuxpkg stable main' | sudo tee /etc/apt/sources.list.d/openhab.list
Now you need to tell the computer / N2 to update it’s list of available software.
apt update
Then you have the last command to install openHAB
apt install openhab -y
When it’s all finished, you just need to start openHAB.
This following line will not only start openHAB, but will start it every time the N2 boots
systemctl enable openhab --now
About 5 minutes later, you can swap to your bigger computer and access openHAB via a web browser
If you’re unsure of the IP address of the N2, just look at the header on screen of the N2 when you boot it.
If you need more information, just read the installation instructions carefully or search this forum.
Good luck