With the release of libnitrokey 3.6 on September 19, this functionality now seems to be officially available upstream. The nitrokey-authenticator package which is an rdep for this mentions in its description "The application supports both, Nitrokey Pro2 and LibremKey. For the latter, however, you need to have libnitrokey version 3.6 or newer" (which is not yet packaged for Debian).
