Hi,
Just tested this as I have ubuntu-mate 17.10 and realised I didn’t have the installer installed. Anyway it installs but doesn’t create a menu item, which is a bit odd as it did in ubuntu-mate 16.04.
Anyway from the terminal try running:
osmcinstaller
Should prompt for sudo password, if not:
sudo osmcinstaller
If it really hasn’t installed then try this from the terminal (assuming on 64 bit, advise if not the case)
wget https://download.opensuse.org/repositories/home:/osmc/xUbuntu_16.04/amd64/osmc-installer_127_amd64.deb
sudo dpkg -i osmc-installer_127_amd64.deb
osmcinstaller
Thanks Tom.