virt-manager

Gnome-Boxes is very simple, yet effective. I think it is on flatpak too. Not sure if it supports ipv6.

I use virt-manager for my lab VMs. Though, don’t discount the power of containers (podman/docker) to isolate and run applications. And lastly, python environments via Conda or venv can create isolated enough environments when doing different things in Python.

Not for virt machines, but toolbox is an easy to use way to keep tooling environments separate from your main machine workspace. Requires/leverages Godmanchester over lxc/docker. It’s a big part of the fedora atomic/immutable stack, to allow you to install things without installing them.

If you want something dead simple then Boxes will do the trick. It doesn’t give you nearly as much flexibility as virt-manager or LXC, etc. but I’ve found it to be capable.

Check out cockpit. https://github.com/cockpit-project/cockpit

Don’t forget that there is a BIOS setting that allows VM to work faster. It’s called virtualization. Search for the setting in your BIOS (it’s called something different across manufacturers). It’s usually located in a menu under “advanced CPU settings” or similar.

It’s often switched off by default.

@Salcie
I haven’t tried many alternatives because Proxmox really seems to be the thing people prefer whether they have a handful of VMs or many more. It has what you ask: web UI, TOTP, ACME to avoid self-signed certs and ofc IPv6 support. It has many options which might be a bit intimidating at first especially for networks, but given its popularity finding tutorials should be easy.

You can create VMs but also LXC containers; I’d recommend using the latter as they consume less resources and can be more straightforwardly configured from Proxmox. You might just need to set some obscure options if you want to run complex Docker setups inside but again tutorials help there.

Hope this helps!