It seems like a hard-fought battle but finally Samsung has acquiesced to the demands of the users of being able to disable the Bixby button. It can now be physically disabled so it would no longer summon up the Bixby Home screen. At first, they disabled it but it could still wake up the phone’s display like the power key would. The latest update though completely disables the button. The caveat, though, is you need to update all Bixby-related apps (Bixby, Bixby Home, and Bixby Service) on your Samsung Galaxy S8, S8 Plus, and Note 8 to the latest version to disable the feature.
Source: Android Authority