I passed on a new Samsung because of the Bixby button. I dont' want it or need it, but I couldn't find a way to remap it... So I returned for an iPhone 8 Plus
I have mine set to open the Google Camera whenever I want, never have any issues with it.
EDIT: So it seems that it is remapable without third-party apps now because of a recent update. That's better.
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[0] - Not without someone I trust vouching for it, at least.
I don't even want to think what else the app might be doing in the background. But that's what they're forcing us to do by having such ridiculous un-disablable behaviour. (note - it was not disableable through any easy let alone delivered means 14 months ago; things may have changed for the better?)
Edit: looks like I can't on my S9, or don't have the latest version...