Yep, Germany in general has a pretty active open source community, so there are already a lot of alternatives out there. Unfortunately, most IT people are bad at marketing, which is why hardly anyone knows about these alternatives.

Their official server in the fediverse (https://social.bund.de/public/local) with currently 99 active government agencies and institutions.

Important addition: You’ll have to set browser.urlbar.update2.engineAliasRefresh to true in about:config to see the option to add search engines via URL. Otherwise you’ll just see the option to remove them and a link to the add-ons page.