Nuendo 6 is unsupported on modern operating systems like Windows 11 or macOS Sonoma. Its original specs include: Soft eLicenser to dongle - Nuendo - Steinberg Forums

Nuendo 6 is a professional audio production software developed by Steinberg, designed for post-production, audio production, and live sound applications. It offers a comprehensive set of tools and features for audio editing, mixing, and mastering.

You can look for a used on forums like KVR Audio or Vi-Control. Ensure the seller performs an official license transfer via Steinberg’s website. Do not buy a "key only" – buy the physical dongle and verify the license is visible in the eLicenser Control Center.