Posting this solution to help others who may come across this problem.
The default rsa KeyPairs generated with the EC2 console appear to be NOT accepted by default on the Ubuntu 22.04 image.
Connection attempts result in a "userauth_pubkey: key type ssh-rsa not in PubkeyAcceptedAlgorithms" message in /usr/log/auth.log
Creating a ECDSA keypair in Puttygen and the copying the public key text (from the top of the PuttyGen screen) into the /home/ubuntu/.ssh/authorized_keys seems to fix the issues I was having.
Hope this helps others !!.