I'm using rootless podman containers when possible (configured with podman generate systemd) and having them always run by enabling linger on my account. Transitioning to a FCOS setup using fcct was easily possible, but I'm forced to use a awkward workaround.

I use trees to import ~/.config/systemd/user and then create a service on first boot that relabels ~/ to the correct owner. My setup would be easier written using the systemd sugar in fcct if user-services were supported.