Unity enables developers to easily build their game for specific (multiple) platforms.
A user in the unity forums discovered, that an export option for a LinuxPlayer is in development.
A member of Unity Technologies then confirmed their plans:
natosha.bard wrote: Hello Everyone,
Vectrex, it seems you've got us on this one
We are in fact working on Linux support to be released initially as a preview feature. We have no set release date yet.