The authorized_keys file specifies the SSH keys that can be used to login to the user of which the file is configured.
This is typically found in each user’s home directory under the .ssh directory: ~/.ssh/authorized_keys. This can be configured using the AuthorizedKeysFile setting in sshd_config.
A deprecated feature of OpenSSH is the authorized_keys2 file. Even though this feature is deprecated, placing keys in ~/ssh/.authorized_keys2 may still work.
https://serverfault.com/questions/116177/whats-the-difference-between-authorized-keys-and-authorized-keys2 https://marc.info/?l=openssh-unix-dev&m=100508718416162&w=2