qemu in 3.5 no longer has an UI
It seems to be compiled without SDL or GTK options so running it straight (e.g. qemu-system-i386 ..) or through aqemu with the intend of using the VM’s display is broken.
I can workaround by using vnc but it is slow and suboptimal.
$ qemu-system-i386 -display sdl$ qemu-system-i386 -display gtk
qemu-system-i386: -display sdl: SDL support is disabled
qemu-system-i386: -display gtk: GTK support is disabled
(from redmine: issue id 6609, created on 2017-01-01, closed on 2017-01-09)