The Bixby button on the Samsung Galaxy S8 can be remapped, here's proof and a tutorial10
2. The app will ask for access to a couple of things, grant it.
3. Once your're inside the app, swipe left to the Hard Keys section and enable the function. Now, you should see a message popping up at the bottom of your screen, click on it.
4. You'll be redirected to the Accessibility Settings screen located in your default settings app.
5. Scroll to the "Services" section at the bottom, locate All in One Gestures and toggle the radio button to ON.
6. Once that is complete, return to the Hard Keys section in All in One Gestures and press the menu button at the top right corner (the three little dots).
7. You should see a single section called "Custom Keys", press it and and an option will appear that will ask you to “Add Custom Key”.
8. Once you see this option, press the Bixby button and the number 1082 should appear. Now press the back button and go to the bottom of the Hard Keys section.
9. There should be a "Key Code" field located below the usual options, 1082 represents the key code for the Bixby Button.
10. Click on it, and choose what action or app you'd like the button to perform/launch. You're all set, enjoy!