For example, I can create a VM on my Mac mini at home that hosts a git repo or even a Forgejo server. A colleague in my Tailnet can then connect to this VM to clone, push or pull source code changes from a coffeeshop or airliner while not exposing the rest of my Mac mini.
Docker Desktop and Podman Desktop are both a treadmill made of Lego bricks.
Have you tried Apple's container CLI[0]? I'm still mostly using OrbStack, but container gives me some hope for the future that Apple cares about this experience.
One thing I noticed though, is that even if I set up the VM as a tagged device with limited access rules, if my host machine (the laptop) is connected as my user (which has less limited permissions), the vm uses my host's user permissions, which isn't really what I want. If I disconnect tailscale on the mac and leave the vm tailscale connected it works as intended though - so that's something to look out for.
Also, if you're using orbstack as an agent sandbox, just be aware that they only recently added an option for true filesystem isolation, the default setup doesn't really sandbox effectively.
I haven’t tried with orbstack, but it is possible to setup containers to use tailscale with kernel networking by mounting /dev/net/tun into the container. With that setup outgoing traffic will automatically route to the tailnet as the container’s device (and you don’t need tailscale on the host at all).
https://robgough.net/multiple-app-instances-with-tailscale
Also has the handy effect of making it super easy to share my dev environment with anyone else on my tailnet, though this could be locked down if needed.
The subdomain routing then works by pointing to that ephemeral machines ip, and my site in dev mode populates the sidebar with active links for this so it's not like I have to keep updating bookmarks etc. Super convenient. It's probably the weakest part of the setup (no https) but works fine for my needs.
Part of that though requires adopting a security model where thats OK. As I’ve started sprinkling MacOS hosts and guests throughout my network, I’ve needed to adopt other vz tactics.
OPs use of Tailscale mirrors my own, but given the security model of OrbStack it’s mostly a convenience rather than a hard security partition within the lan or even the host.