Autodesk's free DWG/DXF viewer and converter DWG TrueView uses a ribbon user interface by default, just like AutoCAD - on which it is based.
To use DWG TrueView in the old, classic UI ("AutoCAD Classic"), download the CUIx file DWGviewr.cuix from Download and copy it to your support folder of the desired version of your DWG TrueView, e.g.
C:\Users\USERNAME\AppData\Roaming\Autodesk\DWG TrueView 2023 - English\R21\enu\Support\dwgviewr.cuix
(for 2021+ versions; backup the original .cuix file)
When you start DWG TrueView, you will now see the classic workspace environment. The first time you run it, you may need to right-click in the area of the original ribbon and select "Close" from the context menu.
