In case there's anyone in this fórum interested in these subjects, I found recently a YouTube channel with some enjoyable videos explaining the collapse of several historical civilizations. I think they are informative and accesible. Personally I appreciate the good English diction of Paul M Cooper and the other narrators. The first episode is devoted to the fall of the Roman Brittania
So far I watched the episodes explaining the collapse of the Viking settlements in Greenland and the Fall of Byzantium (two chapters). I found the channel searching for stuff about the Norse Greenlanders, which is a very recent obsession of mine. Currently I'm reading 'The Greenlanders' by Jane Smiley, a novel written in the style of the Viking sagas