Autodesk offers a 30-day free trial of Civil 3D 2021 (and sometimes 2020 via older links).
If you are a student, teacher, or academic researcher, you can download AutoCAD Civil 3D 2020 for free through the Autodesk Education Program: autodesk autocad civil 3d 2020 free download 2021
If you already own a subscription license for Civil 3D (current version), you can download and install previous versions (including 2020 and 2021) from your Autodesk Account → “All Products & Services” → “View Previous Versions.” Autodesk offers a 30-day free trial of Civil
You cannot, however, legally download only the 2020 version without a valid license key. or academic researcher
