If you are using rootless then it cannot add any iptable rules because only root has the privileges to do that.
And it doesn't sound like you have explicitly setup a firewall either. And since it sporadically works / doesn't work, whatever is happening is probably outside the container itself, a secondary layer like a vpn or custom dns routing or a higher in the network stack (home or external). It could also be based on whatever the container is doing internally, or perhaps doesn't support a consistent rootless setup.
It really depends. But the podman itself appears to be working as expected.
I'd recommend getting help from someone who knows your network stack, or the container owner (unless it is your own) or in general container forums for podman/docker.
Pinned Comments
samarthj commented on 2021-08-23 19:18 (UTC)
quickest way to reach me for changes/updates/issues/pull-requests - https://github.com/samarthj/AUR