LibreTube/app/src/main/res/drawable/ic_fullscreen_exit.xml

<vector xmlns:android="http://schemas.android.com/apk/res/android"
    android:width="24dp"
    android:height="24dp"
    android:tint="@android:color/white"
    android:viewportWidth="24"
    android:viewportHeight="24">
    <path
        android:fillColor="@android:color/white"
        android:pathData="M5,16h3v3h2v-5L5,14v2zM8,8L5,8v2h5L10,5L8,5v3zM14,19h2v-3h3v-2h-5v5zM16,8L16,5h-2v5h5L19,8h-3z" />
</vector>