Hello Guix,
this patch series adds Xpra, along with a few dependencies. I have not tested all the functions (webcam, microphone etc.), but the basic functionality works ("Screen for X11", clipboard sharing).
Note that you may have to add --socket-dir to your commands (xpra --socket-dir=~/.xpra start :200) or you can just add "--socket-dir = ~/.xpra" to ~/.xpra/xpra.conf.