I was unable to login from my old iMac running Yosemite to my new iMac running Ventura using RSA keys. It turns out that RSA key support was disabled in Ventura. To correct the problem, I added the following two lines to the bottom of BOTH /etc/ssh/ssh_config and /etc/ssh/sshd_config on the Ventura side:
Use the ssh-keygen command on a computer to which you’ve downloaded your private key .pem file; for example: First, ensure permissions will allow ssh-keygen to work: chmod 600 /path/to/the/file/your-key-pair.pem Then generate an RSA public key: ssh-keygen -y -f /path/to/the/file/your-key-pair.pem > your-key-pair.pub