This line, at app/03app_gateway_app/main.c:
NRF_RESET_S->NETWORK.FORCEOFF = 0;
Is a hack, but sometimes I need it, and I don't know how. The unwanted behavior is: the network core does not start, or at least the Mira network doesn't work, unless I have the debugger connected (I guess the debugger makes sure the core is started?).