One of the star features of Android 7.1 was native GIF support built into supported keyboards such as Gboard. However, the change didn’t affect the entire system: only the apps that chose to support the feature, kind of like App Shortcuts. And now, as originally spotted by a user of Reddit, it appears that Twitter is building in support for the change as in the latest beta for Android, those running Nougat 7.1 (myself included) can now use the built-in GIF keyboard and avoid using Twitter’s GIF selection tool.
With the feature popping up in the latest beta of the app, you can expect native GIF support in the official Twitter app for Android to arrive for everyone very soon. As is usually the case with updates like these, expect about a week or two to go by before the feature goes public.