Generate Key Pair

ssh-keygen -t ed25519

Add SSH Public Key to Gitlab Profile

You should now login to gitlab preferences->SSH keys and add the ed25519.pub to your SSH Keys.

Add SSH Private Key Path to ~/.ssh/config File

Host gitlab.com
  PreferredAuthentications publickey
  IdentityFile ~/.ssh/ed25519

Debug the connection

ssh -vvv [email protected]

References

1. https://docs.gitlab.com/ee/user/ssh.html