We now disable fakeXinerama on Debian and Ubuntu (r24941) because locating it via ldconfig can take a long time (30 seconds seen on one system with flushed disk cache).
A better solution is to provide a package for it.
There was a regression which was reported here: cocalc : why does Xpra (x11 desktop) take so long to start?, the fix is in r28021.
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/2546