Confirmed in all cases it's just that the X11/Xmir apps can't detect the
session bus address of the login (which is on a different TTY BTW).
Forcing DBUS_SESSION_BUS_ADDRESS solves the problem.
Here are some stack traces of the hangs:
gedit:
(gdb) bt
#0 0x7705e853 in select () at ../sysd
The yakkety fix for bug 1604872 has not solved this. So no longer a
duplicate.
** This bug is no longer a duplicate of bug 1604872
Apps can't connect to the user's session bus, even though it exists
** This bug has been marked a duplicate of bug 1603904
X apps that use dbus (GTK, Firefox) ei