You may want to update your information. Both Ubuntu 14.04 and 16.04 LTS releases are current and supported. Both are supported for 5 years so Ubuntu 14.04 is fully supported until April 2019.
Non LTS releases are only supported for 9 months. As such ownCloud are currently supporting Ubuntu 17.04 which went End of Live in January 2018!
Please fix this. Like many organisations we only use LTS releases and never use them past their EOL however OwnCloud has cut us off :-/
Edit: As releases come out every 6 months however there is only ever an LTS release every 2 years, there will always be 3 releases between each LTS release and always two LTS releases that are supported.