Hm.
Whether I install as Nix-native packages, or using @SergeK 's shell invocation, I still need to have LD_LIBRARY_PATH defined for it to work.
I didn’t realize that when I tried Serge’s shell yesterday.
Edit: it looks like the shell definition in the wiki still requires setting LD_LIBRARY_PATH to work. 
Edit 2: According to @NobbZ , this is not the way to do it.