Suppose I have a publicly available interface, intended to be used exclusively by me or my employees for the purposes of maintenance, e.g. an SSH server.

Since I am processing user's IP address when they make a connection, does GDPR require me to notify the user of such an action in, say a banner shown upon accessing the server?

Additionally, am I obliged to treat possible login attemps and the data entered as personal data?

What if the interface processes user data, but its technology does not necesarily provide for a human-readable interaction, such as an ICMP response?