Multiple people have reported in this forum that the Xioami Redme Note phones do not, however, work with the SmartThings app because of the proprietary operating system that that phone uses. You can find a long discussion of that in the following thread:
App and Xiaomi Redme note 7 phone
So, as always, the first rule of home automation applies: “the model number matters.“ 
Some nonSamsung android phones work just fine with the smartthings app, some need some settings adjustments, and some won’t even install it.