I've tried just about every piece of writing software commonly used, and a bunch of less commonly used ones ones, including a ton of old ones for MS-DOS.

In my subjective opinion, only a few pieces of software really stood out to me.

Scrivener is darn good and hard to beat, it has everything a writer could want in one place as an all in-one-solution. If you're using Linux, Scrivener actually released their last Linux version for free once they stopped developing it, which still works excellent to this day.

There are also a couple Scrivener-alikes that bear mentioning: NovelWriter and SmartEdit Writer.

NovelWriter is one of the few free and open source writing tools that is both stable and supremely functional. It uses a Markdown-like language for formatting (which may be off putting to some, and a positive for others), and has a really nice UI for organizing your story, similar to scrivener. It's not nearly as feature complete as scrivener, but if you don't need those features, NovelWriter is an excellent piece of software.

SmartEdit Writer is a straight up scrivener clone made for Windows, and is also 100% free. It was stable in my testing, the developer is responsive on their website, and its quite polished software overall.

For more traditional word processors, I found the Atlantis Word Processor to be one of the nicest I've ever used. It's extremely performant, stable, incredibly tiny (only 3mb), and has a lovely GUI that's quite customizable. It also works perfectly in Wine if you're using Linux, and I use it as a replacement for LibreOffice. They offer a full paid version, and a fully functional, if less customizable, Lite version for free.

Lastly, there's the Distraction Free writing software, which is a purely barebones affair with very little formatting ability and usually non-WYSIWYG.

Of those, I liked GhostWriter and WriteMonkey. Combined with an organizer/note taking app like CherryTree, you can somewhat effectively emulate a scrivener-like workflow.

And for those curious, though George R.R. Martin still uses Wordstar 4.0 on his old DOS machine, I personally found 99% of DOS word processors to be pretty garbage. They're unintuitive, make it difficult to convert their old formats to something modern and usable, and often have a very specific workflow that is totally alien to modern sensibilities. The only DOS word processor that actually felt modern and was still completely usable (maybe as a more formatting capable distraction free thing?) was WordPerfect 6.2, which was new enough to export RTF files, and utilized IBM's user interface guidelines, which have aged gracefully.