we had a Linux build before launch but ran into some serious issues and frequent crashes so we decided to cut it for now. Hopefully we'll roll it out in future patches.
Tip: If you're using Unity, avoid 2017.3, 2017.4, and 2018.x, they all have serious issues on Linux. If you are on 2017.2 or older you can stay there, otherwise you should upgrade to at least Unity 2019.1.