Hi Daniel,

Thanks for getting back to me with those resources - they gave me another angle to track.

In LibreMesh with have community presets, what we are using here is
freifunk/80211s-sae-bmx7-batadv ie.
https://github.com/libremesh/network-profiles/blob/master/freifunk/80211s-sae-bmx7-batadv/etc/config/lime-defaults

Apart from setting ap_ssid and naming the nodes, no further changes
are made. On some nodes we do change frequency and channel width, to
avoid collisions/overlap with other existing networks. 

Right, I looked at this one and compared it to the LibreMesh/encrypted11s one and they are quite similar.

I built myself an image with this preset and flashed it, unfortunately the same thing happened as before - all interfaces were not sending / receiving and the APs were not visible.

When I manually edited the config to comment out the encryption and key lines, the APs magically came back online.

First of all: Which hardware are you trying to run this on? 

A TP-Link WDD4300 initially

Cheers,
Martin