We just used the new `podmansh` command in the latest version of #podman to shim in using an entirely different container when you login.
Here's #fedora but running an #openSUSE tumbleweed image as the userspace, no extra steps needed.
There's lots of things left to fix (it's an early MVP of course) but I've been able to "switch my terminal userspace" from ubuntu <-> opensuse no problem.