I am still a bit confused by this structure. I would think the food is the subject, but because there is an adjective before the subject, there has to be a formal subject after the verb? Is that correct? Would the adjective take the plural form where there is one?
I think this helps, but I just want to make sure it's the same idea.
I'm not native but I think the sentence pretty much translates to "There is (to be) found a lot of food here", with "här finns det..." being the equivalent to "there is ... here". It is just a fixed expression to say "there is..." like "il y'a ..." (literally "it has here ...") in French or "es gibt ..." (lit. "it gives ...") in German.
So "mat" wouldn't be the subject, but the object (what is to be found) and "det" would be the subject (at least technically). That's how I understand it.
I think "the food is there" then "food" is the subject but in "there is/there are" constructions "there is" is a subject (cuz there isn't one, really, but it's he same as "it is raining") while "food" is either object or predicate nominative... not completely sure in the terminology.
It is a mistery Lukrecija... it is a sacred mistery, in a sense.
Anyway there will be always a lot of different nuances, for the same sentence, to choose from all meaning basically the same thing.
One might say, for example :
(1) Det finns en hel del mat här.
(2) Det finns en massa mat här ( also ... massor av mat .. )
(3) Det finns gott om mat här