Thanks @JPL, @Southside for all the info. Based on your feedback from last week, we have updated the tutorials to recommend using node v8.11.1 (which comes with npm v5.6.0) which is also the version recommended on the nodejs site. From my tests that version works fine on Debian 8 and 9.4, so it seems the problem you faced were related to actually using some version of yarn.
On the other hand, in the tutorials we are not suggesting the use of yarn but just npm, and it was effectively to avoid the need to have an additional dependency, to keep it as simple as possible. I’ll see if I add a comment mentioning that using yarn is totally optional and recommend a version for it which works with nodejs v8.11.1, but users don’t really need yarn for quick starting, specially if they are new to nodejs/npm.