Dollaramas started in Quebec, and have spread all over Canada, but they really are much more heavily concentrated in non-urban settings; have a look at this map:
redliondata.com - Wp content...

If you looked at a population map, Canada is very urbanized, with most of the population in cities within 100km of the southern border, and these Dollarama dots show a lot of stores in small towns a long way from a Walmart. There's one in my small town, and a few more in my region, with no Walmart for 300km ...

While I don't doubt Dollarama has non-urban stores, they aren't primarily a rural or non-urban thing. If you go to the Dollarama site, you can search by city.

dollarama.com - Stores near me

Here are some basic numbers searches I did:

44 DLRs are within 20km of Winnipeg. Manitoba has a few more than 47 DLRs, total.

Alberta has a few more than 154 DLRs. 57 are within 20km of Calgary. A further 51 are within 20km of Edmonton. Another 15 are within 20 km of Red Deer and Lethbridge, combined. So 123 of the 154 and change Albertan DLRs are within 20km of Alberta's four largest municipalities (about 80%).

170 Dollaramas (a hair more than 10% of DLRs 1569 total Canadian stores, per the latest report) are within 30km of Toronto's Union station (i.e., leaving out large chunks of the GTA, or surrounding cities like Hamilton). Another 176 are within 30km of downtown Montreal.

So 20% of stores are within 30km of the downtown cores of Toronto or Montreal. I can go on (61 Ottawa, 47 Hamilton, 47 Quebec city, etc.)

I'd wager the vast majority of the above stores are also within 30km of a Walmart.

Slightly dated source for the rough provincial store counts: statista.com - Number of dollarama stores by province canada