After some experimentation, we found that the "General Export" and "Revit Structure" translators work best. Materials come through correctly now.
Previously, in AC19-20, we found the General translator was never very good, and "Reference Model Export to Revit" (now "Revit Export for Reference Model") gave us the best set of information, including composites. The tables must have turned. Reference Model is now all about geometry, and has stripped much of the information.
Oddly enough, when the Reference Model is opened in Solibri SMV, the composite names and materials are clearly visible. It says each material is 0" thick, which has been addressed on ArchiCAD Talk, but the point is they are in there. They just don't make it into Revit (even using the GS Improved Import).
I'm still not using IFC4 out of fear that Revit can't handle it. Maybe once all of my projects have been updated to the latest AC21 Classifications (note to GS: why couldn't they Migrate into the new Scheme when an older file is opened? AT LEAST assign elements automatically by Tool!).
I still need to do some experimentation to see if the General translator plays nice with advanced geometry like Complex Profiles and SEO's. But for now, that's our choice.
Phoenix, Arizona, USA
ArchiCAD 25 (since 4.5)
Macbook Pro 15" Touchbar OSX 10.15 Core i7 2.9GHz/16GB RAM/Radeon Pro560 4GB