This is a distraction-free, no-frills, locally-runnable writing interface. It's a single HTML file that you can download and run on your machine, with no concerns about trackers, ads, or folks snooping on your writing.
Try it: write.johnellmore.com
Run it yourself: save write.html to your computer and open it.
Pro tip: In Firefox, you can press Cmd+S (Ctrl+S on Windows) to save the page and all of your writing into a single HTML file.