The actual link takes you to a Yahoo page which is allegedly quoting a Telegraph article 1:1. I suppose that's borderline acceptable because an attempt to read a Telegraph article gets you a "Create your free account or log in" message, but the FA should have least carried a link to the original story.
I would have liked to have at least looked at the original article (without an account) to see when it was written and maybe also who wrote it - the Telegraph was taken over by the German "Axel Springer" group a couple of weeks ago.
Looking more closely at the allegations (and only articles from Germany and in German), Rainer Zitelmann compared Hitler with Putin - including pictures of both - and someone apparently took exception and complained to the police. RZ has no idea whether it was a Putin fan, a neo Nazi or whatever who complained. According to his lawyer, it was pretty much a joke and the complainant did not have a leg to stand on, the police agreed and dropped charges citing "insufficient evidence".
I remember discussions on this particular law around 45 years ago (it's nothing new), there had been an anti-Nazi demonstration in Berlin back then and the Police went after some of those involved for "glorifying forbidden symbols" - they showed a Nazi cross with a red line through it on a banner saying "Stop Nazis". This was during the cold war when West Berlin was an island surrounded by East Germany, some of the things the police got up to back then (with backing from the courts) were pretty outrageous - including a murder of a student in a crowd and refusal of medical help to a prisoner with cancer until it was too late. A terrorist group named themselves after the date of that murder and killed a politician or two before fading away, I don't think they were ever caught.
Now to Naomi Seibt and the AfD. I'd never heard of her but Naomi Seibt appears to be a Laura Loomer figure who was under observation by the "MI5 equivalent" as a potential extremist. Whenever there's an extremist political crime in Germany (or the UK for that matter) you will either hear that the perpetrator was under observation or that they were not. That Islamic murderer in Berlin a day or so ago (CSD) had been under observation. I don't know how many people currently have that status, Naomi Seibt used that (and her online friendship with Elon Musk) to claim persecution and go for asylum in the US.
The AfD is a collection of various streams of right-wingers with various motivations, some of them mutually exclusive. Some of the things some of them are calling for (expelling naturalised citizens of a darker hue) are explicitly against the country's constitution - the Nazis withdrew citizenship from Jews back in the day and the constitution explicitly rules that kind of thing out.
Three British MPs have been murdered in the past 11 years. Jo Cox (Labour) by a neo Nazi, someone whose name escapes me (Conservative) by an Islamic terrorist and Ann Widdecombe (Conservative, then Brexit, then "Reform" (Brexit re-branded)). Ann Widdecombe retired years ago, she was a public figure who appeared on TV a lot and was murdered around 3 weeks ago by some weirdo for reasons that I don't think have been made public yet, I believe he was not "under observation".