Linux

None, I use Docker for Linux, and Proton (Heroic) for Windows.

But if I had to pick a virtual machine: libvirt with virt-manager as a frontend, which uses KVM for virtualization.

GNOME Boxes because it doesn't require 5 academic degrees to set up and I'm a GNOME user.

Qemu/KVM and Virt Manager. I have three VMs that I pass my GPU to: a Hackintosh, a Windows 10, and and Windows 7.

virtmanager as frontend for qemu/kvm. I tried the commandline but it's too annoying

KVM

(VMware is proprietary software)

Usually VirtualBox. It's easy and free.

I used KVM with virt-manager for a long time. Even ran a gaming VM with GPU pass-through.

Then I created a Docker image with Linux, Gnome, and novnc so I can spin one up instantly with little resource overhead and control it from any web browser.

KVM + Qemu + libvirt + virt-manager = ❤️

I use virt-manager, aka Virtual Machine Manager. Using this specifically because of the winapps for Linux repo has instructions on how to get Windows apps to run through the VM to be integrated in a Linux environment.

I use qemu, but with Quickemu 'cause I'm lazy lol.

Virtmanger-kvm-qemu

Qemu+Kvm with virt-manager is my boy nowadays. But I'm not a heavy user of Vms, just experimented with this to build some Flatpak. But plan on trying out other distributions, just for science. It wasn't easy to figure out how to share a folder, and I could not get drag and drop or clipboard share to work. Still though, its faster than any other solution. I used VirtualBox in the past, which was easy to work with.

I'm kinda lazy so when I need one, I just use Gnome Boxes and it's pretty easy to setup.

Gnome boxes.

Based on QEMU+KVM so it's quite robust. It works pretty well, plus it has various little features working out of the box that in some other software is a pain in the arse to configure.

Sticks out a bit on my system due to still being GTK3, but there is a GTK4 prototype out that usually works well.

E: downvoting anybody who says Gnome Boxes because you use a different virtual machine frontend is laughably pathetic lmao. Some people in the Linux community are such losers lol

Virtmanager and qemu/kvm

Proxmox seem powerfull

It's a Type1, not Type2
https://en.wikipedia.org/wiki/Hypervisor#Classification

@Mwa qemu :blobfoxcomfycomputer:

So far I’ve been fine with some Oracle Virtualbox and some using the VM Manager that was in my distro or maybe I downloaded it. It’s just called Virtual Machine Manager made by Red Hat. Libvirt.

Between those I’ve been able to do everything I have needed.

You can run a system as a VM on Guix, so yes, that. It's a type-2 hypervisor, as it uses QEMU. Pretty sure this also works for NixOS.

Virt manager for qemu. I use docker and distrobox for Linux distros

I recently managed to use my windows partition (for dual boot) as a disk for a qemu. I don't use it but really cool trick anyways. Tutorial here

Also it's not very healthy for windows since it is not designed for constant hardware changes. But idc all my apps are installed on D: so I can just reinstall it without thinking about it much

Linux: qemu

OpenBSD: vmm, qemu when vmm isn't good enough

Virt-Manager, even works remotely via SSH.

Virtualbox

VirtualBox (desktop for testing and development [Vagrant]), KVM: libvirt, Proxmox (production stuff).

I tried using virt-manager+kvm to try some stuff out the other day but I failed to set-up some crucial things. Probably me being incompetent.

Not like virtualization is a big part of my life anyway. I just wanted to try some other distros and such without rebooting.

If I were to get serious about virtualization I'd need to build a new PC with a second GPU. Then I could stop dual-booting and do everything with VMs. But it'd only be worth it to get serious about learning how to virtualize stuff if I were to do that.