This is a known bug: https://issuetracker.google.com/issues/244400727.

Current workaround is to apply inset paddings manually to FloatingActionButton in landscape orientation.

override fun onCreate(savedInstanceState: Bundle?) {
 ...
 enableEdgeToEdge()
 ...
 setCotent {
  Scaffold(
   floatingActionButton = {
    FloatingActionButton(
     onClick = {},
     modifier = if (LocalConfiguration.current.orientation == Configuration.ORIENTATION_LANDSCAPE) Modifier.windowInsetsPadding(WindowInsets.safeDrawing) else Modifier
    ) {
     Icon(...)
    }
   },
   contentWindowInsets = WindowInsets.safeDrawing
  ) {
   ...
  }
 }
}

The result: