Convert List[Any] to List[Int]

That should be sufficient solution:

l.map(_.toString.toInt)

Starting Scala 2.13 and the introduction of String#toIntOption, we can make @liosedhel's answer a bit safer if needs be:

// val l: List[Any] = List(1, 2, "3")
l.flatMap(_.toString.toIntOption)
// List[Int] = List(1, 2, 3)