Some Galaxy S21, S21+ and S21 Ultra units do not support MST for Samsung Pay.

It looks like availability of the feature varies by country – some get it, others do not, and not in a way that makes much sense.

MST allows the phone to work with point of sale terminals that only support old-school magnetic stripe cards?

This is a big deal in the US where such terminals are quite common, less so in regions where NFC terminals are abundant.

Unfortunately, the S21 phones sold in the US are in the group that does not have MST.

Phones sold in the UK do have it.

The spec sheets from the French, Italian and German press releases make no mention of MST.

The Dutch one does list MST, as does the Polish, Russian and Indian press releases.

The Canadian models are all non-mmWave (as corroborated by their weight and it makes sense, given that the first mmWave auctions were delayed, next is 3.5GHz, so sub-6GHz) a..