[ozzyman]

I just clean install of ubuntu 18.10. And I wanted to install "kodi 17.6" just like I did in 18.04 from stable ppa but when I tried that I couldn't add because I get no release file error.
Ubuntu 18.10 is now available as stable release (since 1 week) so why not you add release file to it.

[wsnipex]

because kodi 17 is 2 years old and users that run non LTS ubuntu that is only 2 weeks old, are encouraged to use v18 beta4 or a nightly