Ronnberg himself uses film or bipolar polarized electrolytic in his build. He doesn’t say anything about the non-polarized on his page.
Note the white stripe that indicates the negative side of the capacitor in this image:
And Here, how to properly connect the bipolar polarized electrolytic:
Following @Dud layout you will also be able to notice the correct polarization:
And as said by @analogoutput, using non-polarized electrolytics will not make any difference.
Link to the original article:
https://web.archive.org/web/20191220104258/http://familjenronnberg.se/~niklas/diy/eurorack/lfo/