for whatever reason, adding this to your platformio.ini env section helps:

[env] lib_compat_mode = strict # default is "soft" 

for whatever reason, adding this to your platformio.ini env section helps:

[env] lib_compat_mode = strict # default is "soft" 

I guess the more clean version would be to add this to your lib_deps

lib_deps = ESP32 Async UDP # important! otherwise "AsyncUDP.h" blabla is missing.. <your libs following>