AgsApplicationContext:main-loop does usually point to an AgsThread implementing AgsMainLoop interface. libags_thread.so provides you the AgsGenericMainLoop object or if you intend to use libags_audio.so, this property shall point to AgsAudioLoop.

However you should rather use AgsThread* ags_concurrency_provider_get_main_loop(AgsConcurrencyProvider*) to obtain the main loop instead.