Getting this implemented and verified would probably require creating a WiFi Beacon transmitter first, in order to have something to validate against. E.g. take the ESP32 French ID transmitter implementation and modify the OUI and the payload format to correspond to the ASD-STAN specification instead.
https://github.com/sxjack/uav_electronic_ids/tree/main/id_france
It should be possible to pick up the data content of the WiFi Beacon messages also on devices that are not running Android 11, via this "hidden" API: https://android.googlesource.com/platform/frameworks/base/+/lollipop-release/wifi/java/android/net/wifi/ScanResult.java#221
Getting this implemented and verified would probably require creating a WiFi Beacon transmitter first, in order to have something to validate against. E.g. take the ESP32 French ID transmitter implementation and modify the OUI and the payload format to correspond to the ASD-STAN specification instead. https://github.com/sxjack/uav_electronic_ids/tree/main/id_france