The current beta xserver-xorg-video package (for amd64/stretch, at least) is essentially empty: it does not contain /usr/lib/xorg/modules/drivers/dummy_drv.so
(It contains only ./usr/share/doc/xserver-xorg-video-dummy/ changelog and copyright files.)
Original ticket is #1215.
Should be fixed by r14573, new beta packages posted.
@dtaylor84: does that work for you?
dummy_drv.so is now installed, unfortunately it doesn't work:
[II] 2016/22/12 11:49:48.358460 XpraServerUtil.process_log_line(ServerSession(:63 - xpra - starting),/usr/lib/xorg/Xorg: symbol lookup error: /usr/lib/xorg/modules/drivers/dummy_drv.so: undefined symbol: dummyModeInit\n)
Sorry about that!
Now actually fixed in r14574, tested and working on both Debian Stretch and Ubuntu Yaketty.
Yep, working for me now, thanks!
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/1384