Germany hasn't had a left-wing extremist movement since the RAF, which was a GDR-affiliated group (or more accurately, a number of groups as the members of the initial Baader-Meinhof group were imprisoned) that performed political assassinations, bombings and abductions initially and then later bank robberies and other less ideologically motivated crimes.

We've been desperately trying to label groups as "left-wing extremist" ever since to avoid having to talk about right-wing terrorism without a comforting "all extremism is bad" caveat. The most recent example is the non-violent eco activist group Last Generation (Letzte Generation) which we've been trying to legally frame as a "criminal organization" (a legal device originally intended to help combat organized crime and terrorist cells) and which politicians and the media have at times referred to as "eco terrorists" and a "green RAF". Keep in mind their stunts mostly consisted of gluing themselves to intersection.

There was a broad "anti-COVID" movement (Querdenker/Querfront - "quer" in this case meaning "traversing (political lines)") founded in 2020 that drew from a broad political base including anti-vaxxers, new agers, "völkisch" nationalists, libertarians/ancaps and some groups self-identifying as leftist. The vast majority of leftist and anarchist movements however strongly opposed this movement, on the one hand because it was strongly affiliated with the political far-right (as a consequence of being a mix of people openly far-right, lying about not being far-right, being politically apathetic or being okay with aligning with the far-right) and on the other because while even anarchists disagreed with the implementation and choice of state anti-COVID measures they often did not disagree with their necessity in principle. These disagreements eventually contributed to Sarah Wagenknecht, a celebrity politician in the minor party Die Linke (The Left) parting ways with her party and founding her own party - although it's noteworthy that the party's official position of refusing to expel her for her publicly stated views led to many people breaking with the party prior to this.

With all that said, I wouldn't put too much trust on the German authorities' ability to correctly assess a terrorist group's ideological positions. According to some other news articles, the group does use left-wing language tho. Apparently it describes itself as being in a battle against "capitalism, patriarchy and colonialism" - which to me sounds more Third Worldist (i.e. Maoist) than anarchist. I can't imagine leftists in Germany broadly welcoming their actions tho as they're providing exactly the boogeyman politicians have been holding up as a justification for cracking down on non-violent "eco terrorists". Anarchists too tend to emphasize the importance of prefiguration before revolution (which is difficult because prefigurative projects also run risk of being labelled "criminal organizations" purely based on ideological stances) so I doubt they're too happy about the association either.