Comment 2 for bug 1036557

I tried connecting to an armh device running LightDM from Remmina using XDMCP and it worked fine. It appears there's no way to set up recent version of GDM to be and XDMCP chooser so I can't reproduce your case. I added some more logging to LightDM to report why it thinks the XDMCP packages aren't valid (and what packets they are).

My guess is they are XDMCP Query packets that either have additional data on the end or more than one packet joined together. As I read the spec these should not be allowed. If you can get a packet capture you may have more luck.

I think GDM upstream no-longer supports this case so if there is a problem a fix may not be used.