Samsung blacklisted other assistant apps from being able to be used by the button. That includes Amazon Alexa and Microsoft Cortana along with Google Assistant. We were able to get around this by using a Tasker script and exporting it as an APK. This means all you need to do is install the app, select it in the settings, and choose Google when you press the button.
This app also supports more than just Google Assistant. We were able to also launch the Cortana app, but it doesn’t work with Amazon Alexa. In theory, any app that supports answering voice commands can be remapped to the button with this method. Any phone that supports Bixby button remapping, including the Galaxy S10/S10+/S10e, Galaxy S9/S9+, and the Galaxy Note 9 and Galaxy Note 8will support using Assistant.
Toggle it on and tap the gear icon to choose an app
Find Bixby Button Assistant Remapper and select it
Press the physical Bixby button and select the assistant app you want to use (click always so it doesn’t ask every time)
It is also possible to do this without the required app by setting up a Bixby quick command. You just set a quick command to “open assistant.” I would recommend the app though, in my testing of the quick command, it wasn’t as fast and it only worked around 20% of the time. Other users have reported very reliable results so your mileage my vary.
How to set up Google Assistant with Quick Commands:
Open up Bixby Voice
Go to Quick Commands in the Bixby dropdown menu
Create a new Quick Command and call it “Assistant”
Set Quick command word or phrase to “assistant”
Select “Type a command”
In this setting, type “open assistant”
Save this Quick Command
Go to Bixby Voice Settings
Select Bixby Key
Select Double press to open Bixby
Select Quick Command
Go to Quick Command options and select “Assistant”
It’s nice that Samsung is finally letting users remap the button to something else. While you can’t fully disable Bixby, you can relegate it to a double-press and put your preferred app to the forefront. Hopefully, Samsung doesn’t do anything in the future to break this workaround.