Is there a tool/tutorial that assumes that I already have a running docker compose setup instead of starting with some toy examples? Basically, I am totally excited about using systemd that I already have on my system instead of adding a new daemon/orchestrator but I feel that the gap between quadlet 101 and migrating quite a complex docker compose YAML to podman/quadlet is quite large.

There was not such a tool when I learned how to do this. Quadlet is relatively new (podman 5) so lots of podman/systemd documentation refers to podman commands that generate systemd unit files. I agree there is a gap.

Search for podlet. It lets you do what you want.

WOW, thank you!

So does this really work for practically any docker compose file you may find in self hostable projects?

I'm still using systemd. Podman keeps telling to use quadlets :)