In the default wiring, D1 is the only unused pin that is easy to work with. D2 is used for CE so using it to blink a led as well will not work.

Thank you for the idea. I try and I will do a report. But is there a way to start the sketch after a delay even if the gateway does not find the broker. I understand that this is not very interesting .... except for my library. With a node, it is possible to start the sketch after a delay with the parameter MY_TRANSPORT_WAIT_READY_MS. Thank you.