I'm not sure whether he's a member or not, but that he's a supporter is being reported on German TV by official sources. As are his anti-Islamist views, here's the summary from
Der Spiegel (Google translated):
In the meantime, however, he seems to have drifted away in his activism. On his account at X in November, he posted four "demands of liberal Saudi opposition," the first point: "Germany must protect its borders against illegal migration." It has been shown that "the open border policy was a plan of Merkel to Islamize Europe," he wrote in relation to the former Chancellor. In other entries, he openly sympathized with the AfD and dreamed of a joint project with the largely right-wing extremist party: an academy for ex-Muslims. "Who else is fighting Islam in Germany?" he asked.
In a video interview released eight days ago on an anti-Islam US blog A. over 45 minutes of crude theses: The German state is conducting a "covert secret operation" in order to "hunt and destroy their lives worldwide, Saudi Arabian ex-Muslims". At the same time, Syrian jihadists were granted asylum in Germany.
I see a fifth person has now died