qualle337

No PoE at that end, I just bought a cheap splitter off AliExpress for a few bucks to separate the Ethernet from power at that end.
 
Yep, using same W5100 module.  Not even a "shield" I just connected it with dupont wires.  But a shield is probably a more reliable connection, now that I think about it.

Yes it's a bit of an architectural change.  But one I actually prefer.  In fact, I have MQTT server running on one SBC, controller (OpenHAB in my case) running on another, etc...  But you could just as easily containerize things (and one day I probably will, too).
 
You can also position the gateway in a more ideal location (for the radio).  Mine is centrally located in our home.  I actually bought a PoE switch and run the power and data to it all in one wire.

Yes - looks like you're right! Thanks for pointing me in this direction. I'll update the thread when I found a solution (other than plugging in the Arduino after the boot) in case someone else has similar issues.

Cheers,
Julius