Loading *.adf files into QGIS?

Arcinfo .adf files can be raster or vector.

Try QGIS' Add Vector Layer, select source types of Directory and ArcInfo Binary Coverage, and then select the directory containing the .adf files. There will be second dialog asking which sub-layers to add; coverages are a composite datatype that can contain any combination of points, lines, polygons, and annotation.

You can also add the .adf file directly, without choosing the directory type, but then you don't get to choose which geometry to load.

For background info see Arcinfo Binary Grid format and Arcinfo Binary Coverage format pages.

I downloaded some data in adf format from https://www.eea.europa.eu/data-and-maps. I have been able to load it into QGIS as follows: - add raster layer - select filetype: Arc/Info Binary Grid (hdr.adf etc.) Straight to GIS, smoothly, no problem.