You can install Dark Mode Everywhere from the Chrome Web Store.

Click on the puzzle icon in the top right corner of the browser and pin Dark Mode Everywhere to the toolbar, so it's always at hand.

Click on the Dark Mode Everywhere icon in the toolbar to open the pop-up window.

Click one of the buttons to turn dark mode on or off. By default, dark mode is set to auto, and it's automatically turned on for all websites.

Open the keyboard shortcuts settings by going to chrome://extensions/shortcuts, and add shortcuts for the actions you use the most.

You can enable the extension to work in incognito mode by going to chrome://extensions, and opening the extension details and checking the Allow in incognito toggle.