Mysterious SSH Password Disable Bug on Ubuntu 24.04

Disabling SSH password access over the internet while allowing it on the local LAN on an Ubuntu 24.04 server seemed straightforward using sshd_config. However, a custom configuration file in /etc/ssh/sshd_config.d/ was ignored after restarting the SSH daemon. The culprit was sshd_config's 'first-come, first-served' configuration rule, and a system-generated '50-cloud-init.conf' file containing 'PasswordAuthentication yes', which loaded before the custom file. Renaming the custom configuration file to '10-no-passwords.conf' solved the problem by ensuring it loaded first.