Host foobar foobar.example.com
  Hostname foobar.example.com
  IdentityFile ~/.ssh/id_ed25519

Host *
  IdentityFile ~/.ssh/id_ed25519
  IdentityFile ~/.ssh/id_rsa

$ ssh -Tv bob@foobar
debug1: Reading configuration data /h//.ssh/config
debug1: ~/.ssh/config line 49: Applying options for foobar
debug1: ~/.ssh/config line 63: Applying options for *
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: ~/.ssh/id_rsa
debug1: Authentications that can continue: publickey
debug1: Offering ED25519 public key: ~/.ssh/id_ed25519
debug1: Server accepts key: pkalg ssh-ed25519 blen 51
debug1: Authentication succeeded (publickey).