Hello @togsin
If you are looking to implement a local communication between 3 Nodes and a local Concentrator. You have to use 4 nodes one of them as a concentrator and the other 3 as an end node. The Gateway can't be a local concentrator, his job is always to collect data from different LoRa Nodes and share them on a connected Server. You can use 4 Nucleo-L073 to do this job. But personally, I recommend you use 4 Nucleo-WL55JC1 and use this example or the one on this video to start your application. If you still want to use the Nucleo-L073, you have to migrate one of those example to be compatible with those nodes. For that, use the AN5408.
Best Regards.
STTwo-32