This is a really good way for German service providers to offer alternatives to the common US based IdPs in their products without much additional overhead regarding implementation.
The blog post has been removed because it wouldn’t currently work anymore, as Verimi now requires mTLS, which Auth0 doesn’t support yet.
However, there’s still a github repo available fyi - GitHub - auth0-blog/auth0-verimi-sample: Auth0 Verimi Sample.