let's try this again...

ci/push-package.template.yml

@@ -5,7 +5,7 @@
       - mkdir -p ~/.ssh
       - 'command -v ssh-agent >/dev/null || ( apt-get update -y && apt-get install openssh-client -y )'
       - eval $(ssh-agent -s)
-      - echo $SSH_PRIVATE_KEY > ~/.ssh/id_ed25519
+      - echo "$SSH_PRIVATE_KEY" | tr -d '\r' > ~/.ssh/id_ed25519
       - chmod 400 ~/.ssh/id_ed25519
       - ssh-add ~/.ssh/id_ed25519
       - chmod 700 ~/.ssh