When Samsung published this patent on fingerprint readers under a display, it seemed like the Galaxy S9 may get one. It didn't, so rumors moved on to the Galaxy Note9. Even the reliable Ming-Chi Kuo from KGI predicted that the 2018 Note will finally pull it off. Then new rumors suggested otherwise. Kuo has changed his stance and now agrees with the rumors. Samsung allegedly canceled this feature because neither the ultrasonic reader (by Qualcomm) nor the optical reader (by Samsung LSI, Synaptics and others) failed to meet the company's technical requirements. Even so, KGI is confident...
Source: https://www.gsmarena.com/galaxy_note9_will_not_have_a_fingerprint_reader_under_its_display-news-30021.php
