If you are an avid PC gamer, you probably know about Discord. It started out as a chat service for gamers, but it has seen immense growth since then among regular users as well. Due to Discord's popularity as a chat service, the mobile apps for Android and iOS are also quite popular among consumers. While the Android app may have had a dark theme for a while now, Discord has quietly added a new AMOLED dark theme in the latest version (9.8.2 and later) of its Android app. The new dark theme may feel more pleasurable than the current "Dark" theme for some users but it is unlikely that the new theme will prolong the battery life on your phones.
Currently available on version 9.8.2 or later, the hidden "AMOLED optimized (experimental)" option can be accessed in Settings -> Appearance where you will need to tap on the "Dark" option ten times. You should see a toast notification that says, "Brave one, the path to darkness opens!". Then, the hidden option will be visible under the "Light" and "Dark" options.
After the setting is enabled, app needs to be restarted so that the theme can be applied to nearly all of the UI elements. Unfortunately right now, AMOLED dark doesn't support all UI elements. Nevertheless, you don't need a phone running Android 10 to access the new dark theme but if you do, make sure that the theme isn't tied to the dark mode on Android 10.