The default style on osm.ch now includes contour lines and is updated to the latest version of the openstreetmap-carto style sheet.
Elevation data created from a mash-up of SRTM and ASTER GDEM data. ASTER GDEM is a product of METI and NASA. Post processing was kindly provided by Yves Cainaud from opensnowmap.org.
I’m one of the developers of osm-carto. Do you publish your fork somewhere, possibly with instructions how to add the elevation data and where they are available? I’d like to experiment a bit with adding them (it’s related to this ticket: https://github.com/gravitystorm/openstreetmap-carto/issues/2931 ).
Yes the fork is under the sosm organisation: https://github.com/sosm/openstreetmap-carto
As explained in the post we use the data as preprocessed by Yves Cainaud from opensnowmap.org, though limited to Switzerland. I can send you what we have. There are currently no public instructions, though it is quite easy. The hillshading is just a file which needs to be placed next to the style, and the contour lines are imported using shp2pgsql into a dedicated table.