As of February 28, Bixby was updated on the Galaxy S8, S9 and Galaxy Note8 and Note9 devices running on Samsung's One UI (Android 9) allowing the dedicated Bixby button to be remapped to a custom action or app. You still can't totally disable Bixby, but you can at least set Bixby to a double press so that it won't be as easy to accidentally trigger. You can then set the single-press to open any app or set a custom action that you wish such as calling a contact or toggling Wi-Fi. It was discovered, however, that Samsung blacklisted certain apps, specifically competing voice...
Source: https://www.gsmarena.com/you_can_set_google_assistant_to_the_bixby_key_with_a_new_workaround-news-35800.php
