probably has not been enabled in this firmware, because the firmware is the setting page of the DST

it is not strange, sometimes all of the sites are not updated, but the firmware is for the whole world, it is so. if you do not believe me, try asking for information to support global tp-link by...

this firmware is good for all countries ;)

is not true, it is a firmware that is good for all, I'm Italian, I installed it and it works without problems

in the changelog are almost never written any changes you have made in the firmware, so an update could also solve.

the firmware is located here: http://www.tplink.com/resources/software/TD-W8980_V1_140408.zip