As long as they are tied to the RPG
The Warhammer (both Fantasy and 40k) lore is a mess. Many things are spread out among the board/card games, novels, PC games, tabletop army books, and the RPGs. As long as the question asks about the RPGsRPG aspect, it is on topic. This might or might not include bits from other than the RPG books as sources, but the question needs to solve an RPG-related question.
As a simple example, asking about the stance of Faction A to Faction B could be a valid lore question if described as solving an RPG question. But asking for what equipment Unit X has without showing the RPG-relation would be presumably Wargame-centric and off-topic.
This is similar to Legend of the 5 rings, where there is an old CCG, an LCG, novels, and the RPGs. These share a world and lore, but not all things are elaborated everywhere similarly. At times cards or novel lore holds tiny bits that the RPG doesn't tell about, but which can inform a good answer that tries to solve an RPG-related issue. One example is the number of toes for dragons needed for a description of one, where the best answer is the card-art which has canon value in L5R. However, in such cases, it can help to establish a ranking in which order sources are deemed authoritative.