The current recommendation api is is unmaintained and hads legacy code written about 10 years ago.
Souce code: https://github.com/wikimedia/research-recommendation-api/
Recently Machine learning team updated it to a usable stage and API is hosted at Liftwing. But it is not ready for any feature additions or enhancements due to old architecture and code.
As per T367873: Technical exploration to support topic-based suggestions with the current Recommendation API, language team wish to take over the codebase, modernize and add topic based suggestion feature.
This require codebase modernization - remove unused code, fix dependencies. fix tooling, fix CI/CD and so on.