Google on its Android system has been trying to enforce dark mode in all applications for some time. Twitter was another application adapted for the dark theme. Dark mode has already appeared in Twitter on iOS, and the same change was announced for Android users a few months ago. In the latest alpha version of Twitter marked with 8.19.0 number, developers of the app finally added a dark theme to their main application.
If you have the latest alpha version of the Twitter application on your phone, you can turn on the dark theme after entering Settings, where in the "Image and sound" section there is a separate menu regarding this mode. To get access to this version of the application you must be a part of the official Twitter development program and you can join it on the official Google's forum. It is worth remembering that in case of problems in using the new function, the solution may be to clear the cache.