Samsung's Game Tuner app hasn't been updated since December 2018, so the following information might not surprise anyone, but the company officially terminated Game Tuner yesterday, April 30. The app is still listed on the Galaxy Store and Play Store, but it is no longer available for download and the app's description has been changed to reflect the termination.
Game Tuner was a mobile gaming-centric app containing features such as an FPS limiter, per-app brightness and texture quality settings, a resolution downscaler and more.
Game Tuner says goodbye, Game Plugins says hello
Samsung's mobile game-tuning app was quite useful, especially for non-flagship phones and users who may have wanted to boost performance at the expense of graphical fidelity. But since Game Tuner stopped being updated almost two years ago, it's been slowly phased out in favor of Samsung's newer game-centric app Game Plugins. The Game Plugins Plus module, in particular, offers per-app graphics settings such as a downscaler and FPS limiters. In other words, it offers more or less the same features as Game Tuner.
For now, Galaxy users who still have Game Tuner installed on their device can continue to use the app, as long as the device runs Android Oreo and not a more recent OS version. Otherwise, if you want to go deeper under the hood of your mobile games and force them to run a certain way, you'll have to rely on Game Plugins moving forward.