Pretty much a newb at VMs. Previous experience only includes Virtualbox on a Windows Host for older DOS apps, trying out upgrades in Debian Testing or Sid, and trying out unique distributions for their focused functionality. However, at this time, I would like to create VMs inside both a Debian Linux desktop and server environment. Wow, VMs solve a host of issues even for the home user.

Here goes:

I have a dual booting desktop system with 11 Pro and a Debian installation tracking Bookworm presently. Installed are QEMU, KVM, and Xen (have yet to boot into Xen and configure) as a test bed. Virtual managers installed include Aqemu, Boxes, and Virt-Manager.

Goals:
1) To create a server using Xen with virtual machines comprising (1) Openmediavault and (2) a Debian based firewall.

2) Create virtual machines on the desktop for DOS and trying out upgrades and combinations of software before committing them to the host OS.

3) Implement snapshots.

4) Learn PCI-passthrough implementation for future projects (I've been bitten).

Questions:
1) Having found no definitive answer online, which virtual machine manager is best for the XEN server, XEN desktop? Virt-Manager appears to be the obvious choice. When trying to find pros and cons, all I could find was info regarding poor performance in Virt-Manager for what ever reason without listing an alternative.

2) Anyone with experience with Aqemu? Is it dead? Does it have the capability to manage/create both type 1 and 2 hypervisors for the desktop?

3) Would keeping Boxes around offer any advantage for the quick installation over say Virt-Manager or Aqemu?

4) Which, Virt-Manager, Aqemu, or alternative is best for PCI-passthrough, Secure Boot (TPM), and Nvidia drivers?

Yup, I'm a newb; please handle with kiddy gloves or not. Just learning about SSH (so you know I'm a newb!)

This is going to draw so many opinions (so I'll throw mine in first).

For the W11 system, I would get rid of dual boot and run VirtualBox. This lets you share easily and have all your apps running at the same time. It does require a lot of memory. I did this for years on a business laptop with 16M to do Linux development but have all my Office apps on the second monitor.

Under Linux, I've done everything with bash scripts and qemu/kvm config. But I'm a command-line guy. I guess virsh/virt-manager has an easier way to do passthru than:
For bare metal I've only used ESXi with web browser, but I've heard good things about XCP-ng for Xen and mean to try it.

There are three machines presently. The first's primary function is generally productivity, education, gaming, etc. It is a Beast Canyon Nuc w/3080 running W11 with an installation of Virtualbox. Virtualbox is used for running old DOS programs and trying out upgrades to Debian Testing before committing on the second machine. Also, every now and then I decide to try out a new distro for whatever reason.

Somewhere along the way, machine learning caught my attention. So, I decided to go full in because of two sons and gaming--though they have consoles, they wouldn't have to fight over one system.

The second machine which I'm using now dual boots Debian and Windows 11 Pro with Secure Boot enabled. It consists of an EVGA Z590 Dark, 11900KF, two NVLinked 3090 GPUs... The W11Pro installed is a mirror of that of the Beast Canyon with an newer version of Office Pro Plus. The games' drive for the Windows installation consists of two SSDs striped. Debian is also installed on the same NVMe and has all the same programs as Windows minus Office; it is additionally set up for a project or two in machine learning (real reason for the build). It also consists of a Blu-Ray drive and several mechanical hard drives.

The third machine is a 3Beez Music Management System. It runs Ubuntu and proprietary software/hardware for music playback. Because of the amount of storage it contains and other factors, I'd like to use it as a server running Xen. With a CPU upgrade, it could accommodate two virtual machines. It is also a silent PC with no fans whatsoever. One would be a firewall and the other Openmediavault. That way I could keep the firewall and NAS separate--security. As an aside, back in my second B.S. days, I ran a 3.5" industrial motherboard with a Debian installation from compact flash used as a wireless router and firewall. Those were fun days.

It will have been a chore running back and forth with flash media and USB drives, as each of the desktop machines has its own backup solution. Even though, I've a router that can handle these chores, it's limited by USB 3.0 and a 1Gb connectivity. These machines have 2.5Gb Ethernet connectivity, and I'd like to take advantage of the speed.

I was just wondering from experience, what are the pros and cons of AQemu and Virt-Manager? I've initially decided to use Boxes for DOS and Windows because of perceived ease of use. However for Xen, which would be better from usability and performance between AQemu and Virt-Manager? The processor upgrade will be from Intel's 7th generation, maximum power but staying under the cooling solutions max thermal design power dissipation.

Yeah, I was long winded! I just wanted those who might respond, to intimately know my use cases. Maybe I just have to get in there and play.

I will be backing up the 3Beez's BIOS (customizations galore for quiet operation of the 6GB of storage in mechanical drives), system NVMe, and mechanical drives in case I'd like to return it to stock.

Tried Gnome Boxes:

1) Did not want a preconfigured bloated system, so installed vm with debian 11 minimal netinstall letting Boxes do the heavy lifting. What I thought would be a configuration file for the vm being downloaded was in fact an entire distribution with equivalent of tasksel, Desktop Environment, and Gnome Desktop, the same as downloading a preconfigured system, an option I chose to defer. I quickly deleted that vm and elected to...

2) Same option to install with downloaded debian 11 minimum installation media, but chose to go through the installation manually indicating only basic system utilities in tasksel. Voila!

3) The plan--cloning the basic minimal installation for use trying new features, repositories... That didn't go so well. After trying to start the cloned vm, greeted with contents in first attachment.

Metadata from the config file of the base installation:
Metadata from the cloned installation:
At first glance, all that I can discern is the difference in <media>. Replacing the cloned <media> with the original did not change the outcome.

Bug?
Normal behavior?

Would I expect the same with Aqemu or Virt-Manager? Anything I did wrong or forgot to install? I thought that Boxes was supposed to be the easy no frills solution. Yeah, yadda yadda yadda; Virtual Box in Windows gets it right. Should I just uninstall Boxes and try Aqemu? On this machine, I don't need the power of Virt-Manager, at least yet. I'd really like to use the built in kernel features and apt.

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