I know that in France they often use mercredi, miel, mince as euphemism for merde. Do people in Quebec use the same words, or perhaps different ones?
Wiktionnaire says "marde" is a "déformation phonétique" de "merde". In the latter entry, you will find interesting usage notes explaining that in some instances in Canada you'll hear a speaker using "merde" but the construction will differ "[sujet] à' marde" vs. "[sujet] de merde"; according to the same entry, "marde" was not entirely unknown in France, albeit more than a century ago.
That being said, this is not about the interjection. My experience is that I basically never use "marde" alone to curse like you would hear someone in France say "Merde !". I will resort to using... "Merde !" too in that context, or use a swear word (crisse, tabarnac, ostie etc.) or even "fuck" (which is considerably less potent a word than it is in English when used in my sociolect). Of course these mince nothing. I see there is also "merdre" with the extra "r" which is a pleasing variation, but I would never go through the lengths of using this, as it requires some effort with the pronunciation to sound this "r".
So in a way in Quebec/Canadian French you could argue the interjection "merde" is a minced form for the "marde" because of what I explained. As for the quality of an object or a situation, it depends, "cochonnerie", which is not Quebec/Canada-specific, comes to mind, for products especially. The loanword "scrap" is though : "c'est de la scrap". There must be many others.
Canadian won't use "marde", because their culture is slightly different from the French one. A French will "jure" (swear) (using all sort of words such as "merde", "putain", "bordel", etc...) while a Quebecers will sacre. Meanings a Canadian will say "tabarnak", "Estie", "Calice", etc...
To sacre come from the christian's language, and to not blashpeme they used euphemism such as:
For the most famous Note that there is no official spelling for those euphemism, everybody can write Estie like he want (because the goal is to say "Hostie" without actually saying it).
So in a nutshell: a Quebecer will never use "marde" or even "merde".