Whatever happened to the Angles in Anglia, on the Jutland Peninsula, after many of them moved to the island of Great Britain. Did they all move to Great Britain? Is there any evidence of them, i.e. language, culture, genetics, etc., in that region in Germany or Denmark today?
If you believe Bede, they all left, and that area was for a time deserted before the Danes settled there.
“the country which is called Anglia, and which is said, from that time, to remain desert to this day”
The only subsequent mention of them on the continent is in a Frankish document from the early 800s, Lex Anglorum et Werinorum hoc est Thuringorum, 'The law of the Angles and Warini, that is the Thuringians".
That suggests that the remaining Angles united with the Warini (or Varini), moved south into what is today Germany, and became known as the Thuringians. Tacitus, in the first century CE, mentions the Varini as a tribe living near the Angli.
Presumably any remaining traces of them would be found in the German state of Thuringia.
Mind that there is actually a fairly decent chance that conceptions of the “Angles” that have survived until modern times bore little real relationship to the actual Germanic people who lived in that region. Tacitus mentions a tribe he calls the Anglii. Bede’s history has always had an overwhelming influence on how people thought about the settlement of Germanic peoples into Great Britain because his history is quite high quality for the time period and the most significant and complete of such work that exists. However Bede likely conflated facts and myths fairly regularly in his writings, and also likely based much of what he wrote on themselves flawed writings from a few generations prior that no longer survive. Bede was writing 300 years or more after the Germanic settlement into Britain had begun and that’s a difficult span of time to pierce via scholarship alone.
It seems like given the reputation Bede’s works had in his own lifetime and immediately after, and how durable they remained, he probably succeeded in capturing the best knowledge of the time about the matter, but that isn’t the same as having accurately portrayed the history. Bede would have been familiar with Roman writers and would have been influenced in how they frequently described Germanic tribes–which was usually to group them in ways that did not always map with how those peoples might group themselves.
All this is to say it’s not at all outside the realm of possibility there was never a people in Germany/Denmark who called themselves the “Angles” (or any of the various forms that word would have taken 1500 years ago in a different language than English), that word could just describe a grouping of tribes with a common dialect, who likely would have referred to themselves along more specific tribal lines. This same phenomenon is seen even contemporary to Bede himself, he basically coined the term Anglo-Saxon, but the peoples of Anglo-Saxon Britain in Bede’s time likely never referred to themselves as such. There was a conception of some of the Kingdoms in the Heptarchy being “Anglian” vs “Saxon”, albeit even then it is likely that most people living in those Kingdoms used more specific terminology for themselves.
I follow the AskHistorians subreddit and there was a high quality write up on some tangential matters relating to this around a year ago that could be worth reading: (1) What did the Anglo-Saxons call themselves? : AskHistorians (reddit.com)
Interestingly it is highly likely Alfred the Great himself and other early rulers of a quasi-united England used the term Anglo-Saxon specifically because of the awareness they would have had of Bede’s writings, and the value they would have seen in the term sort of helping in their efforts to unify the ancestral Kingdoms of England.
The very ethnic identifiers with specific Kingdoms in the Heptarchy correlating with specific predecessor Germanic tribes around the modern Day Denmark/Northern Germany region, likely was Bede formalizing knowledge at the time, but that knowledge likely was itself flawed and the peoples of these kingdoms likely had no true, rigorously preserved information on where the fuck they had come from. They had traditions and conceptions, if you’ve ever done any genealogy work you know how easily these things develop. My family had a powerful belief (in my father’s line / the line of my surname) that we entered the United States from Canada in the late 19th century and it was “well known” by the entire extended family this was true. Actual genealogical research instead shows this ancestry was flawed, my family has a long line of farm laborers in it (men who worked farms but lacked the means to own their own), one of which moved to Canada for a time and had his son born there, but then moved back. This movement created the false idea that the family was originally from Canada, in fact we have history of living in the United States for a good 100 years prior to that ancestor moving his family into Canada and back into the United States in the 1880s.
This is something that was widely believed by a lot of people in an era of written records when these things can be researched. Imagine the multigenerational “drift” in received family lore about one’s origins in an era with no written records.