One thing I don't like about Podman is that it pretends to be docker-compatible while having some minor differences that will come to bite you. And users of your docker-based project who try to run it on Podman will come to you and complain.
As such, most of the fixes for Podman/Docker incompatibilities is just addressing that assumption with a few extra flags on the Podman commands to change how the user namespace maps between the container and the host, etc etc.
Making the changes required to run under rootless is often very simple.
Try having a docker-compose with a service that waits until a dependency is healthy --- in a host that has no systemd (such as Alpine Linux).
The service will never start because Podman relies on systemd (and only systemd) to do the periodic healthchecks which it needs to do in order to handle such dependencies.
And of course, this fact isn't adequately documented anywhere. And Red Hat says they'll never, ever drop this dependency.
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But I don't know if there are any tools compatible with the Docker ecosystem other than Podman. I'd love to find one.
For anyone curious, there's more details on why this is tricky to do with Podman at https://github.com/podman-container-tools/podman/pull/27033 .
Most recently: Netavark doesn't match Docker's behavior with accepting broadcast traffic on a published port.