Man pages matching name al_run_detached_thread in section 3alleg5:

al_run_detached_thread.3alleg5.en	debian 10 / allegro5-doc
al_run_detached_thread.3alleg5.en	debian 11 / allegro5-doc
al_run_detached_thread.3alleg5.en	debian 12 / allegro5-doc