I'm guessing the podman node needs to be running podman v2 also? The yum repos on my RHEL7/8 VMs only have v1 (1.6.4 and 1.9.3) currently.
I adding a connection on my macOS laptop using the following command
podman system connection add tnealrh8 --identity ~/.ssh/foo.pem --socket-path /run/podman/io.podman ssh://root@XX.XX.XX.XX
I specified the socket-path because the default values ('/run/podman/podman.sock' or '/run/user/{uid}/podman/podman.sock) did not exist. But cannot connect.
$ podman images
Error: Failed to create sshClient: Connection to bastion host (ssh://root@XX.XX.XX.XX:22/run/podman/io.podman) failed.: ssh: handshake failed: ssh: unable to authenticate, attempted methods [none publickey], no supported methods remain