@CharredChar I had issues with the Option 66 and 67. I needed to set the DHCP Next Server option to my TFTP server IP under Advanced Setting in the DHCP configuration.

  @Hank21 Thanks for noting that. I upgraded that day to ensure it wasn't an issue with older firmware so I did not expect there to be another one available. It took a little time but I saw it come up. I updated it again (it is now on 2.3.2 Build 20251029 Rel.12727) but the issue persists.

  @GamerMine Yes, I understand. Option 66 is supposed to be the address to the PXE (TFTP) server and Option 67 the file to load.
Unfortunately the Omada controllers seem to have a long standing issue where even if you enter anything into Option 66 it will continue to only send the IP address of the router itself during the request. Which, honestly, I wouldn't even care of being an issue if I could make it act as the server anyway.

The only exception is putting the ER605 controller into stand-alone mode, removing it from the Omada Controller, and configuring it directly on the router. I am not willing to do this as the whole point is to have a single location for management using the Omada Controller. If this simple feature is not available (with over 3 years of the issue being known) even though it is advertised as capable I'd consider that an unacceptable failure which alone is enough to question ever using TP-Link hardware at a new site I build or manage. This might sound like strong wording but every response in the past has been, "I'll be done soon." And the original poster is satisfied enough to drop it. This has cause there to be a half-dozen threads that end up with no actual answers to the problem and it's been ignored.

  @CharredChar I completely agree with you. It should work as advertised. My solution is more like a workaround to this issue but not the fix to it. Option 66 should be fixed by the TP-Link team to work as intended without any workaround. This is strange that it hasn't been fixed already because it does not seems complicated, that's a DHCP option like the others.

I think that TP-Link firmware are Open Source because these are based on OpenWRT so I might take a look at the sources to see what's going on.

By the way here is the equipment I use:

Model: ER605

Hardware Version: v2.20

Firmware Version: 2.3.3 Build 20251029 Rel.18054

I confirm having the same problem.