If you actually have i915 graphics, you might want to install a couple of packages. Run 'lspci' to check. In my experience, it will still work without that. I'm not sure if you miss anything that way - I don't do anything that requires intense graphics. Just simple games and video here.

$ apt-cache search i915
xserver-xorg-video-intel - X.Org X server -- Intel i8xx, i9xx display driver
firmware-intel-graphics - Binary firmware for Intel iGPUs and IPUs

I don't know the solution, but you could try the options in the failsafe boot one at a time, or eliminate them one at a time until you find the one that makes the difference. I would start with just adding 'nomodeset' to the default boot command. That one is often useful to eliminate black screen.

BETTER SOLUTION:
I used your command and added '-vga qxl' and the desktop comes up.

qemu-system-x86_64 -enable-kvm -m 2048 -nic user,model=virtio -vga qxl -cdrom isos/devuan_excalibur_6.1.1_amd64_desktop-live.iso

Make sure you have xserver-xorg-video-qxl installed.

I'm not seeing that problem in my seatd test iso:
https://get.refracta.org/files/experime … 4_1517.iso

I can add a mouse after boot and it works, and I can boot with the mouse plugged in, unplug and replug it and it works again. I'm running the iso from a live-usb for this test.

That one has seatd without elogind or consolekit and without a display manager. (also no turnstile in that one)

I haven't used live-build in over 10 years and never on devuan. I know there are some people who have used it with devuan.
Devuan live-sdk is similar to live-build in that it pulls packages from the repo and builds the system in a chroot. This is good if you're making a lot of different isos - you just need to alter the configs to do a different build. The downside is that you often don't know the build failed until the end of the run, then you have to start over. When you start building a new release, you can have frequent failures in the beginning because some packages in your list might not be in the repo anymore or may have changed names.

refractasnapshot does not require access to the repo to build the iso. It makes a copy of your running system with a few things excluded and puts that into the iso. Since it's copying an installed system, any questions about missing packages have already been answered before you started to make the iso. Also, since it's copying the running system, any changes you make right before running it will be copied into the iso. The downside of this method is that you must have an installed system, either on hardware or in a virtual machine, for each flavor you want to build.

To adjust what gets copied by refractasnapshot, edit /usr/lib/refractasnapshot/snapshot_exclude.list. See 'man rsync' for details.

Edit: one more difference between live-build or live-sdk and refractasnapshot is that refractasnapshot builds an iso that has an unprivileged user with a home directory. The others do not, but the live-config scripts create the user and home when the system boots. This affects which live-config options are used in the boot command. See 'man live-config' and probably 'man live-boot' too.
Note that live-build, live-sdk and refractasnapshot all use the debian live-boot and live-config scripts.

I don't know what those others are.

Devuan 5 is daedalus (oldstable), Devuan 6 is excalibur (stable). Gnome works in excalibur. If you want to try it in freia (currently in testing) there's a netinstall iso, so you could install it to a spare partition or into a virtual machine. And if you do that, please let us know what you find. Thanks.

I've used this in the past as /etc/asoundrc to get firefox to use jack. Haven't tried it lately.

pcm.!default {
    type plug
    slave { pcm "jack" }
}

pcm.jack {
    type jack
    playback_ports {
        0 system:playback_1
        1 system:playback_2
    }
    capture_ports {
        0 system:capture_1
        1 system:capture_2
    }
}

ctl.mixer0 {
    type hw
    card 0
}

I call it set-default-card.  Put it in /usr/local/bin or somewhere else that's in root's path. Make it executable. Run it with or without the card number or with and without the usb audio device as many times as you want. It replaces the lines in asound.conf and restarts alsa so it takes effect.

Package-Name         Component            Required/Optional   
libtool              base                 REQUIRED            
cups-devel           base                 REQUIRED            
cups-image           base                 REQUIRED            
libusb               base                 REQUIRED            
python3-pyqt4-dbus   gui_qt4              OPTIONAL            
python3-pyqt4        gui_qt4              REQUIRED            
python3-devel        base                 REQUIRED            

The only package in that list that I could find in excalibur is libtool. Either they are looking for a specific version, or they don't know where to find libtool in a debian system. There is a libusb-0.1.4 and a libusb-1.0.0 in excalibur, but those either don't match the script's search pattern or they are the wrong version. Or again, maybe they don't know where to look. The others don't exist.

Also, most development packages in debian/devuan end in -dev, not -devel. There are a few libcups*-dev packages. Whoever wrote that script doesn't know that.

Why is it on sourceforge instead of some HP website?

I forgot to ask what graphics card you have. Run lspci to see that.

- Look in /var/log/Xorg.0.log for lines with (EE) to see if there are any errors.

- Look in /var/log/apt/history.log to see if any graphics related packages got upgraded.

- Look in /etc/lightdm/lightdm.conf to see if the two autologin lines are uncommented and have the correct user name. Make sure you scroll down to the [Seat:*] section and not in the extensive comments section above.

- Before you run startx, log in as root and run service lightdm status. If it's not running, try starting it, and if it's running, try restarting it. service lightdm start or service lightdm stop && service lightdm start (I can never get 'restart' to work.)

Refracta has

- few metapackages and excludes Recommends to make it leaner and easier to remove packages to customize the system. It used to fit on one CD.
- added diagnostic, rescue and repair tools, mostly cli.
- a few config tweaks - kernel.sysrq=1 in sysctl.conf, ADD_EXTRA_GROUPS in adduser.conf, ALWAYS_SET_PATH yes in /etc/default/su and a few others.
- openssh-server running so you can log in remotely if there's no display. NOTE: The world knows your password. You should be behind a router and not have port forwarding set up or else unplug the network cable.
- Refracta is older than Devuan. That's why the version numbers match Debian's.

I feel like I'm forgetting something, but those are the main differences.

Yes, that way will work if you don't want to use qemu or virtualbox. Another way would be to  use a spare partition on your hard drive instead of external storage media, but those are essentially the same thing.

It should work with whatever is in your apt sources and do the same as using apt or apt-get to update and upgrade.