The Feldjäger are the German Military Police. This Volkswagen Toureg was a prototype for a contest. According to A_Sinclaire on Reddit,
That was just a prototype presented by VW, but it did not meet the criteria of the GFK1 tender and VW withdrew the concept. In the end the Mercedes G class based Enok won. They also don’t have that turret.
The turret is mounted to the roof rack of the Toureg. Not sure how long it will last on there. The LMG platform is remotely controlled.
The “turret” is an FLW100 (Fernbedienbare Leichte Waffenstation – remotely-controlled light weapon-platform) produced by KMW, which can be mounted to practically any vehicle.