Etiquette at Hindu kovils and mosques is it the same as Buddhist temples

Different in important ways. For Hindu kovils (very common in Jaffna, the north and the hill country tea estates): remove shoes and hats, cover shoulders and knees, and at many kovils men must also remove their shirts at the inner sanctum, while women avoid going during menstruation by traditional rule. Cameras are usually fine in the courtyard but often forbidden inside the inner shrine, ask. For mosques: cover shoulders, knees AND head for women (bring a scarf), remove shoes; some mosques allow non-Muslim visitors during non-prayer times only, others not at all, so always ask the caretaker first. Avoid Friday midday prayers entirely. The universal rule across all three faiths: never turn your back to or pose for selfies with the deity/Buddha/mihrab.