I did, twice…
Will try out that ENV var thing.
Note: the home directory is the same as before on my older computer, so evidently there’s some stuff in my home directory that makes IJulia think it’s already set up to work with the older install.
At this point, having done the whole conda thing, it’s probably best if I just leave it alone and don’t touch things that aren’t actually broken (yet) 
It is in fact running the conda based install.