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> I'm curious how well docker on top of the Ubuntu vm works.

Works well enough. Better than Docker on barebone MacOS if you have lot of file access in a volume.

That's one of the thing which surprised me when I started using VMs to develop. First time was with a postgres backed app: I expected to lose performance when moving everything in a VM. But got the exact opposite result at the time. Postgres really liked the linux filesystem more than the windows one, enough to do more than offset the VM tax.

I work directly in my guest os and clone my projects and run them in there. There are some projects that are driven through docker-compose and that works nicely. The one caveat is that I had to install `apt install binfmt-support qemu-user-static` so that docker can run x86_64 images on my arm64 VM.

docker in a VM works fine because docker isn't a VM and just uses Linux features like pivot-root, namespaces, and cgroups to isolate programs. At least on x86 CPUs you can even do nested virtualization if the CPU supports it.