EndNote is widely used with Microsoft Word, but it can be used with a range of other word-processors with Windows or Mac OS or LaTeX.
Read about setting up and working with LibreOffice Writer
Read about setting up and working with Pages
Note that LaTeX users usually use Bibtex: it is still useful to have EndNote collect and manage your references, then export them to LaTeX. Download instructions and an output style for working with LaTeX here.
To check software compatibility, look at this article.