Why a problem? Thread is meant for discussion, glad you bumped it up.
Only protector fully compatible is Whitestone dome (for $55) and that's a very complicated protector to install and very expensive too, but it's compatible with a LOT of cases.
However, AMT who is importing Whitestone dome for S9, doesn't have it for S8/Note8 so you may have to get it yourself from Amazon.
The generic ones available in the market aren't compatible with a lot of cases, especially tight fitting ones since they push up on the protector either cracking it or causing it to lift up.