hello everyone I know that installing on windows server 2012 r2 is not supported, I have a domain all our servers are windows I don't know if installing owncloud on linux will allow the users in windows domain access own cloud with their existing accounts I don't need to create a new users for them is it possible or I have to search for alternative software that support integration with Active Directory
The choose of the used linux distro is up to you. There should be some webpages / wikis out there explaining you the differences between ubuntu desktop or server.
Desktop version often already include a GUI which is not needed on a server. If you don't want to update your Ubuntu system very often, rather go for the LTS version.