In order to deploy using SSH, we need a SSH keypair. Please use an algorithm strong enough and also supported by GHA and your remote host.
You can use the command below to generate a keypair:
ssh-keygen -t ed25519 -C gha@vm-YourLogin -f ~/.ssh/id_gha
For this use case, don't use a passphrase (just type Return to select an empty passphrase).