Yes, the Kindle Paperwhite Signature Edition (2021) has a dark mode. This mode inverts the text and background so that the background is black and the text is white. This makes it easier to read in dark environments and is less distracting for others. To activate Dark Mode, you can swipe down from the top of the screen and press the Dark Mode switch or use the "Invert black and white" switch in the settings under "Accessibility".