LK LiquidSkin Clear Film 3-pack ($5)
Lightning Knight is another brand with great reviews for past Samsung smartphone protectors. So, get this cheap 3-pack knowing that you'll probably have no problem putting this on your Galaxy Note 9.
If you want quantity, for just $5 you get three Galaxy Note 9 screen protectors. And while they're just a cheap film, they do use a military-grade TPU material that's super durable. In the box, you'll get the wet-application system, squeegee, and other tools to help you install it with ease.
LK claims each protector is 99.9% clear and is flexible, tough, won't discolor over time, and has self-healing properties to magically get rid of small scratches.