A freshly-submitted patent for Samsung may shed new light on how the company plans to handle fingerprint authentication in 2019. The good news is: it is in the display. The bad news is that it may not be the more state-of-the-art ultrasound version bandied about in previous speculations.
https://www.notebookcheck.net/New-Samsung-patent-may-bring-optical-in-display-fingerprint-scanner-to-Galaxy-S10-after-all.339266.0.html