The language pack installer essentially overlays new resource files onto the existing installation directory. It does not reinstall the core kernel of AutoCAD 2021. The process is generally non-invasive and takes significantly less time than a full installation.
: Ensure all instances of AutoCAD are closed during the installation to avoid errors. How to Switch Languages After Installation language pack autocad 2021 free
AutoCAD LT 2021 also supports Language Packs, but the download link is separate. Ensure you grab the pack, or the installer will fail. or the installer will fail.