Hi Dan,
My machines do not give me that warning anymore. I could NOT remember what I did to make this warning go away. I think I just found it. In my Config.g I have one line that says this…
M555 P2 ; Set Firmware mode to Marlin
I looked it up and this is all it says… M555 - Duet3D (dozuki.com)
But I think that may be what got rid of that warning message.