It would be very easy for me to say that publishing is an industry, and that the reason I don't make enough money to even think about telling people I am an author when they ask the ubiquitously depressing get-to-know-you question is because I haven't invested in marketing or my platform, but I won't say that even though I just did.
When I first started writing my novel it was in LibreOffice Writer, but I quickly realized that while it worked well for essays and even my thesis, it was not ideal for writing fiction. At least, not for me. I wanted something stable and flexible enough to handle tens of thousands of words of dark, realistic fantasy. In addition, I wanted to make sure that when those tens of thousands of words were ready for publishing, I could convert the manuscript fairly easily from a single master file.
This guide is what I wish I had when I started, and I'm putting it together in case anyone else is curious or wants to use free and open source software to write and publish their novel.