Since my last post, I did the following:
- burnt a new RPI image using the rpi imager
- Installed the RAK gateway with the newest image and edited the global_conf.json in two ways:
a) changed the address to: eu1.cloud.thethings.network
b) exchanged the whole .json file with the one generated by v3.
Both didn’t show me a successful connection. What is the recommended way? I guess b) - taking the one of v3.
The service is running fine:
The EUI was correctly inserted in the local_config.json during installation.
@descartes
Thanks, that did it…
I was a bit irritated by the documentation that suggests the EUI is kind of optional now ( Gateway EUI (if your gateway has an EUI).
Anyways, it’s working, feeling bad after bothering @bluejedi als 
:
don’t ban me please.