Writers may be interested to know that the free open source Scrivener-clone Manuskript has today popped out a Manuskript 0.8 version for Windows. Until Scrivener 3 for Windows finally appears ($45, 2019?), Manuskript is the best option for Windows desktops for fiction writers.
Though not for serious non-fiction. I’ve looked all over its UI and the wiki / changelog / website and it seems to completely lack a footnotes system or any plan for one. Scribus is useless at footnotes, and while Affinity Publisher is free it is still stuck in a footnote-less and buggy beta. So if you need open source software it seems your only currently-developed option for non-fiction is LibreOffice Writer.
The first thing you’ll want to do in Manuskript, when trying it, is change the tiny squished font in the main writer. Font settings are not easy to find initially, but are down in: Edit | Settings | Views | Text Editor | Font. You can also change padding, line-spacing, background colour and more. The full-screen view has its own font and background controls, also found by digging into the same Settings panel. Don’t accept the clunky defaults, and figure on spending about 30 minutes setting up the UI and fonts.
With Pandoc installed it can import more file formats than it supports ‘out of the box’.