Man pages matching name al_init_primitives_addon in section 3alleg5:

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