Apparently, Skydemon only displays the Tower Frequency of the Ramstein (ETAR) CTR. However, there is a special Awareness Campaign from the Airbase to use the Ramstein GCA frequency for position reports around the CTR. Unfortunately, the frequency isn't included into SD. Would be great to have this also available directly in the App.

The "Ramstein GCA" frequency is 124,275. They are not only responsible for the GCA approaches, but also for the airspace around the Ramstein CTR, which is class E and G. To improve safety around the CTR, where some heavy IFR traffic can occur, pilots should report their position on the Ramstein GCA frequency. The goal with with this, is to prevent of getting a class D TMA in the region.

Here some more details in English: https://www.ramstein.af.mil/News/Article-Display/Article/305304/safety-first/

And German: https://www.lsvrp.de/ramstein-awareness-kampagne-bleibt-aktuell/