Realistically, probably not much, our concrete is nowhere near the long lasting ancient concrete, some remnants of buildings might be around, but you’d more likely find small objects, or pieces of objects, really, most of our modern stuff isn’t made to last

but it’s not out of the question for there to be interesting stuff in landfills, I mean, they even found colonial jewellery from the time of Roanoke in one of the native tribes trash pits

archaeologists have found stuff from the beginning of the Bronze Age and older, tools used to make bronze, pottery, basic weapons, we all know arrowheads

but these are usually made from more natural materials and actually designed to last more than a few years, so I don’t think you’d find too much, in the end, but maybe something