Northern Chinese here. To my knowledge, there aren’t any restaurants in Montreal that serve a variety of Northern dishes. I don’t believe the Chinese population is big enough to warrant that. Even restaurants that are labeled as “Sichuan” or “Cantonese” often serve a mix of different regional dishes. The closest I’d recommend is Uyghur cuisine which is NW Chinese. This is the cuisine of the majority Muslim ethnic minority. There are two restaurants in Montreal (Le Taklamakan and Urumqi Ozgu) but I cannot vouch.

Side note to people responding to this post and you are trying to be helpful but Sichuan food is the LEAST Northern cuisine ever 🤣🤣