What, you mean that multiplying by 8/5 is too difficult? (double it 4 times and divide by 10 - it becomes easier with practice).
Alternatively, you could always use Waze via Android Auto, and have it display the speed in km/hr on the Satnav display. Not ideal, but a workaround of sorts.
Seriously though, I agree that for the want of a few lines of code, which they could have ported from one of their other models, such an omission is unforgivable.
You do get the impression that Kia never expected to sell many Niros in the UK, so they just didn't put the effort in to the UK model first time around. The facelift model model might be different a different proposition though.
All Kia Niro related discussions