I could never figure out how to use virt-manager, so I just use plain qemu. Something like this to boot the iso file from your hard drive...

qemu-system-x86_64 -enable-kvm -m 2048 -cdrom devuan_whatever.iso 

Change the 2048 to however much RAM you want to give it (in MB)

Edit: Fixed typo.

It's not clear what you want to accomplish.

1. If your usb stick is set up with a persistent volume to save changes in the live system, you can install qemu in it. If you don't have persistence set up, you would be better off making a new live-usb with a system that has qemu installed.

2. If you want to install qemu, it would be easier to install it from the devuan repo instead of compiling it from source.

3. Where is the other OS you want to boot? Are you planning to install it into a VM inside your live system? Is there a virtual hard disk with a system already on it?

Most of our packages are from debian, unchanged. That includes python3-venv.

Sometimes an update or upgrade will fail if you happen to hit a mirror when it's updating itself. In this case, trying after a few minutes will fix it.

Please post your /etc/apt/sources.list to make sure it's correct.

Refracta isos have openssh-server installed; the devuan-live isos do not. That's why you can't ssh to the devuan box.

How did you start Thunderbird in a live session? It's not in the isos. Did you install it in the live session? If so, you may have run out of memory.

I went to www.cepher.net and looked inside. I'd say there's a problem with that website. Turning the pages of the book uses 213% of the cpu in a VM that has been allotted 2 cores. It didn't lock up, but it was acting like it was close to doing so.

Install sysv-rc-conf and run it (as root) in a terminal. Arrow keys to navigate, space bar to select/unselect and q to quit.

And while you're in that root terminal...

less /var/log/syslog

In the rc1 live isos, -updates and -security are already enabled in sources.list. Just update the sources and install runit-init. If you want to keep refractasnapshot and refractainstaller, then also install live-config-runit at the same time.

# apt update
# apt upgrade
# apt install runit-init live-config-runit

apt remove gtk3-nocsd libgtk3-nocsd

Tested on desktop-live iso.

You have to remove libgtk3-nocsd. Just getting rid of the main package doesn't fix it.

This one was locally brewed - Simple Update Notifier
https://dev1galaxy.org/viewtopic.php?pid=32990#p32990

IMPORTANT!!!
The live installer does not know how to re-use an existing /home partition. You have to arrange it manually.
If you select an existing /home partition with the live installer, it will be formatted and you will lose your data.
(Exception is if you set the installer not to format any partitions, and you format all of them in advance, but even then, some of your desktop configs may get clobbered with the new versions.)

Install without choosing a separate partition for /home.
Then rename the new /home directory.
Make a new /home directory.
Edit /etc/fstab to mount the old home partition to the new /home directory.

You can do the above tasks while still in the live session or after rebooting into single user mode. If you need more specific directions, let us know what your partition layout looks like so we can use the correct device names.

It might be possible to do that by pinning online sources to lower priority than the file or dvd source. Then you would need to specify the online source with the -t option to get packages from there.

As time goes on, any packages you pull from online sources will be more likely to need newer versions of associated packages that are in the dvd source, so that the package in the dvd won't be installable.

I think another way to do it is to mount the iso file and add it as a cdrom source.

Did you boot legacy bios or uefi? If you did boot legacy bios, did you create a bios_grub partition?

I just tried expert install with the same iso and ran into some problems. I used gpt partition table but did not create the bios_grub partition. The installer didn't warn me about it, but I did get the window that asks if I want to install grub.

I answered No and it proceeded to ask me where I wanted grub installed. I chose "Select location" and didn't put in any location. It tried to install grub to nowhere.  (Says so in the log)

When the window came up asking me to finish, I selected Go Back. The screen flashed a few times and it came back to the finish window. I tried to go back to the menu several times, but eventually I had to choose Finish the Install.

Use 'su -' instead of just 'su' to become root. That way you will get root's $PATH.

The other way to fix this is to use the full path to the command... 

/usr/sbin/dpkg-reconfigure...

See 'man su' for yet another solution.