Modifying the lensfun xml files would work as well,
until the next update of the lensfun database or exiv2.
Afaik, the actual lens name is not stored in the image metadata (improbable or impossible for 3rd party lenses anyway…), it’s the exiv2 library that generates the lens name from the lens ID taking into account the camera brand. Each manufacturer has its own IDs for his lenses…