Basic defense against Stingray type devices is to disable 2G in your settings. In theory, you may not have coverage when only 2G is available. In practice, it is 2025.
Why would that have anything to do with it? Surely LEOs have LTE or 5G simulators by now. Even if they're not "on the market" I would bet they are just sold privately.
Am I looking at the wrong place in AOSP? To me it looks like it only needs 2.2.
https://cs.android.com/android/platform/superproject/main/+/...