When bin/client runs and an ed25519 key is picked up from ~/.ssh, it fails with:
[ssh-connection]: Failed (IllegalStateException) to execute: Failed (NoSuchAlgorithmException)
to load key from /home/<user>/.ssh/id_ed25519: Unsupported key type (ssh-ed25519) in /home/<user>/.ssh/id_ed25519
No command is executed and the client exits with status 1, even when username and password are given on the command line, because publickey authentication is attempted before password and the key load error aborts the connection.
ed25519 is OpenSSH's default key type since 7.8, so this hits any user whose ~/.ssh contains a default key. RSA keys work fine, which is probably why it went unnoticed.
When bin/client runs and an ed25519 key is picked up from ~/.ssh, it fails with:
No command is executed and the client exits with status 1, even when username and password are given on the command line, because publickey authentication is attempted before password and the key load error aborts the connection.
ed25519 is OpenSSH's default key type since 7.8, so this hits any user whose ~/.ssh contains a default key. RSA keys work fine, which is probably why it went unnoticed.