Asked earlier today in the Open Data StackExchange, and quickly responded to with a chunk of SPARQL, with a few interesting additional replies on Twitter.
Seems to aptly summarize the state of the nation. Check with the crowd, be wary of dupes and errors, to get the official data be ready to jump through some hoops 
One more solution (in the „fun hack“ category) to this, would be to sample the digital height model at the coordinates of each commune, i.e. using
Though one also wonders why there is no simply formatted, accessible open dataset summarizing this map…
https://www.bfs.admin.ch/bfs/de/home/grundlagen/agvch.assetdetail.11407588.html