In American English, a canteen can be 3 things: 1) A place like a cafeteria, where many people get their food and eat together. 2) A bar 3) a flask for carrying liquids to drink, for example a container for drinking water on a hike in the mountains. We don't use this word very often, but I hear it in older movies or movies about the military. Good luck!

Interesting that they use both terms in that article. In this case I suspect the dining-room is for senior admin staff or teachers. Possibly the food is served to them, as opposed to a canteen where you collect it as you pay.

In a school, a canteen is where you buy food from. In the US school system, you'd probably call this a cafeteria. The dining room is where you would sit down and eat it.

The article may be correctly distinguishing between a canteen (meaning 2 = a container used for carrying water by military personell) and a dinning room. But ı have not seen the article

Your example is old. I don’t know what they are referring too, either. A canteen is very bare bones, like in the military. Maybe in the old days they had a place for the servants, the canteen?? But I’ve never heard of a house or even a school having a canteen. I’m confused.