So, concerning Low German, is it a sub-classification of North Sea Germanic or Low Saxon-Low Franconian? Glottolog and Wikipedia say the former, Ethnologue says the latter.
I would say that it is Low Saxon – Low Franconian. Low Saxon in Germany anyway for all intents and purposes is Low German. This somewhat includes Dutch Low Saxon, but not so much anymore, as it seems to have merged a lot with Low Franconian. Low Franconian is just Dutch. Middle Franconian is more like Ripaurian and Moselle Franconian Middle German to the south and southeast of the Netherlands in the part of Germany near the Netherlands, Belgium, Luxembourg and Northeastern France near the Lorraine.
I do not even kn ow what North Sea Germanic even is – is that Ingaevonic? That’s almost English – but Low German is nearly English itself – the Angles, Saxons and especially the Jutes spoke something like English, and South Jutnish, probably a separate language from Danish spoken in southeastern Denmark, is supposedly nearly intelligible with Scots!
At one time there was a “North Sea Fisherman’s Language” which was something like Ingaevonic, and they could all understand each other. Either their own speech was close enough to each other or they all adopted this sort of jargon based on their speech and that of the other North Sea fishermen, but at any rate, when they spoke this Sailor’s or Fisherman’s language, they could understand each other and sailors and fishermen could communicate with each other in all of the ports of the North Sea regardless of where they came from.