I don't know about DXF file specifically, but there are a couple of AutoCAD viewers discussed on my page here:
ActiveX Plugin: How to view AutoCAD .DWG .DWF etc. files
Doing a quick search for "AutoCAD preview handler" also found this newer option, although it looks like it only gives you a fixed 2D preview, not one you can rotate etc. I haven't tried this one but if it's installed and working in Explorer, it should also work in Opus (as long as the file extensions haven't been explicitly assigned to another viewer, e.g. via the other linked steps above): The Longbow Previewer 2017 (V4).