Can't complete Learn from the Nguni as Mutapa

[LIBER-TEA!!!!!]

I've completed all the other missions for Mutapa/Zimbabwe but I can't complete the last one as there is only one province (on the entire map) with Nguni culture. Did I click the wrong button on an earlier pop up or am I missing a way of changing some provinces to have the culture.

The mission objective is to have 4 provinces with 5 base manpower and culture of Nguni.

[grotaclas]

There are 12 provinces with Nguni culture at the start of the game(see https://eu4.paradoxwikis.com/Political_list_of_provinces ). But only one of them is colonized at the start of the game. I'm not sure if it is possible to keep the culture in the current version. A quick test seems to indicate that the culture only changes when the province has a land connection to the capital.
Or you could culture convert provinces.If you don't have the DLC to culture convert to an adjacent culture,you could change your primary culture to Nguni.
Or you could choose the option to make Zulu a march in the event from the previous mission. Then you have a subject with Nguni as primary culture and you just have to hope that they choose an idea or advisor which gives them at least 5% discipline(they get another 5% from their ambition) and make them big enough so that they have 20 force limit.
Or you could get a vassal which already has +10% discipline from ideas and make them go bankrupt as an OPM in the province with Nguni culture. That will give them the primary culture and religion of their province.