Try without flags

src/freedombone-image-customise

 
     # configure DNS
     resolvconf=$rootdir/var/run/NetworkManager/resolv.conf
-    chattr -i $resolvconf
     echo 'domain localdomain' > $resolvconf
     echo 'search localdomain' >> $resolvconf
     echo "nameserver $NAMESERVER1" >> $resolvconf
     echo "nameserver $NAMESERVER4" >> $resolvconf
     echo "nameserver $NAMESERVER5" >> $resolvconf
     echo "nameserver $NAMESERVER6" >> $resolvconf
-    chattr +i $resolvconf
 
     if [[ $VARIANT != "meshclient" && $VARIANT != "meshusb" ]]; then
         # change the motd to show further install instructions