I tried:
sudo add-apt-repository ppa:neon/kf5
sudo apt-get update
sudo apt-get install project-neon5-session project-neon5-utils project-neon5-konsole project-neon5-breeze project-neon5-plasma-workspace-wallpapers
but I get this error:
No JSON object could be decoded
How can I install KDE 5.2 or 5.3 on Linux Mint 17.1 KDE?