※ I am largely a non-fiction writer. Mostly I write technical papers, presentations, and blog posts. These tools might not work for you. YMMV.

Below please find my primary writing tools.

GNU Emacs, Org-mode, and various add-ons (cross platform, open formats, free)

Emacs is my main tool for writing. Org helps me structure it and do other things. I use aspell for spell checking.

DevonTHINK (MacOS, open formats, expensive)

When I want to save and organize references I find on-line I save them to PDFs in DT.

BeOrg (iOS/iPadOS/WatchOS, open formats, free + paid add-ons)

This is one of my mobile capture tools.

DevonTHINK To Go (iOS/iPadOS, open formats, free-ish)

This is my other mobile capture tool.

NextCloud (cross platform, open formats, free*)

I have an instance I pay for that is outside the normal cloud infrastructure. I also am standing up my own personal private instance.

Home Network Attached Storage (NAS) (cross platform, all formats, expensive)

I have a complicated NAS setup at home. It is there largely so I can keep local copies of media.

Physical books (analog, paper, varies)

I regularly make use of different dictionaries, references, and odd bits of books.

White boards (analog, ephemeral, varies)

I mind map and note take and do other things on white boards. I never seem to have enough.