Why not fork X11 and add right-wing politics?

Interesting that you focus on the "DEI" slogan term, and not stuff like him claiming mRNA vaccines are turning people into mutants, or the general ineptitude of his untested commits breaking things in the past, and the overall disrespect in his attitude documented here.

While the term "DEI" is not really used in Germany - outside of people bandwagoning American politics - there certainly are cases of affirmative action in the broad sense of "anything that aims to provide additional help to discriminated groups beyond providing equal conditions". Even simple stuff like the by now long-running "Girls' Day" promoting professions with low quotas of women to female students with specialised events here in Germany falls under that umbrella. As does Schleswig-Holstein having a minority party (SSW) for the Danish minority with special rights. As do special privileges for Sorbs in Eastern Germany. So I am even uncertain what exactly you want to express with there being "no DEI" here.

And policies like that are not that uncommon in other parts of Europe, too - especially those with a more intense colonial history than Germany.

No, I think in this case, Enrico Weigelt is just someone who genuinely went down the (Proto)-fascist pipeline in the last years, and probably has a bit of additional issues looking at his behaviour beyond that. I doubt this is special to Europe/Germany.

Except that's not true. We have the AGG (Allgemeines Gleichbehandlungs-Gesetz) which has the same goals and then some as DEI.