My Chinese Redmi 4A showed me a step counter in the screen to the left of the home screen but my non-Chinese Redmi 6 does not
I found the answer myself after some Googling. This is a feature of the China ROM that is not present in the non-China ROM.

MIUI Forum: [Feature Request] Step counter absent!

This feature was reported missing since at least January 2018. So far I haven't found anything on whether it's going to be added to the non-China ROM.