Samsung will let you remap the Bixby button on older phones too
 

If the Bixby button on your Samsung Galaxy phone doesn't get much use, you might prefer to make it open another app. Samsung noted the remapping option when it revealed the S10 lineup this week, but if you have a slightly older Galaxy phone (namely,...

https://www.engadget.com/2019/02/22/...stomize-remap/