LibreOffice FTW. https://libreoffice.org/ It may be glitchy in some areas, but I've been using it since graduating high school, and I can do whatever I want with it.
I used libre office for years, but I switched for 2 reasons. 1: the export to docx had problems, and most publications require your submissions to be in docx format; 2: it gets laggy with large documents. This lag becomes distracting when writing novels. Seems to start around page 20-50 and gets worse and worse as you go. I wish I had better alternatives to suggest. I wish that publishers would stop demanding we subm…
There will be a learning curve but I find my attention stays on the content, as I'm not continually distracted by the format issues that are better delayed until the text is complete.
You'll want a reasonable text editor with spell checker, preferably one that knows to ignore formatting commands. Note you will end up with PDF output - if you really have to submit docx, my condolences!