https://thenextweb.com/facebook/2020/02/14/facebook-lite-gets-dark-mode-while-the-main-app-is-still-waiting/

Just about every major app is implementing some kind of Dark Mode these days, but there’s one notable omission: Facebook. We saw the company test a dark mode for Android in August and a dark desktop UI in October, but there’s been no permanent option yet. Now it seems the company is finally ready to join the slew of stealthy apps, as it’s begun rolling out dark mode to Facebook Lite, as spotted by Android Police.

Though I’m not seeing it on my own device yet, the option has appeared for several users. It should appear as a toggle right beneath the ‘Settings’ button of the hamburger menu.