I did get things working successfully after some effort. The knowledge is in here but would need to be untangled to be useful to others.
Viewing the GUI desktop of the Raspberry Pi from another computer.
A remote desktop thing.
I didn't really take notes on rdesktop itself, though I had significant exposure through some of my projects with it. See /tag/rdesktop. Apparently I didn't note an rdesktop version.
check out SeamlessRDP mode. It does what I was using xpra for.