I've been using this method for years. Very simple, and gets the job done. Most websites and desktop apps default to whites and off-whites which convert perfect

I've been using this method for years. Very simple, and gets the job done. Most websites and desktop apps default to whites and off-whites which convert perfectly to blacks and off-blacks when enabled. Pocket, Firefox, and FBReader on my Android devices all have dark modes for reading on my mobile devices; takes care of all my use-cases!