why Samsung pay not available in m series ?

[Muk38sh]

I want use Samsung pay but not available in my mobile Samsung galaxy m20 :( 

also i can't side load

[Samsungm51knox]

i could see that while my phone (galaxy m51) restarts, it shows that its secured by knox, also i see the knox secured icon for secure folder. Please clarify why m51 doesn't support samsung pay, if knox is the only issue