So I've been going back through my writing folder and exporting every scrivener project from the last 8 years because the Linux version is no longer in development and it don't work post Ubuntu 16.04.

PROPRIETARY FORMATS ARE BAD, M'KAY?

There's so many projects *falls over*

@vamp vim + pandoc FTFW. Markdown, HTML, LaTeX.

It's actually amazingly simple to get started. I'd picked up HTML, LaTeX, and Markdown in that order, mostly use the latter for starting out, though I'll tune in one of the others if necessary.

Pandoc handles conversions and publishing: to any of the above, PDF, ePub, .mobi, DJVU, and more.

I've found that pandoc and the rest work quite well in a work-flow as long as I'm the only one writing and editing. But for anything that requires collaboration, a document gets shared in a word processor format, and then that's where it usually stays while being edited and until being published.
@jcn9k Charlie Stross writes on that problem.
@dredmorbius pandoc is a marvellous tool. After my Scrivener export mission, I've now got a bunch of rtf files, some with formatting, some without (depending on how old they are). I hate rtf, love markdown. Pandoc to the rescue! (fun fact: Pandoc was the first CLI tool I ever used, way back when I was still running Windows)