MuseScore 2 for Ubuntu 14.04 and above

The latest stable release of MuseScore is available from the PPA on Launchpad:

It works on Ubuntu 14.04, 15.04 and related Debian distributions, including Mint.

Run the following code from the terminal to install or upgrade MuseScore to version 2.0.3:

# To add the PPA if you don't already have it:
sudo add-apt-repository ppa:mscore-ubuntu/mscore-stable

# To install or upgrade MuseScore:
sudo apt-get update
sudo apt-get install musescore

Note: once you add the PPA upgrades will usually happen automatically, but the upgrade to 2.0.3 will not be automatic on some systems because it's dependencies (the other packages it relies on) have changed since 2.0.0. This is normal behaviour and a stability feature of the apt-get upgrade mechanism.