Thanks, Jim.
It was Xibalba, at xibalba.l33t.codes.44510. I actually didn't create an account, so I didn't log in, but it is the initial greeting that gives the warning.
Going to the telnet BBS Guide and searching for SSH shows a number of [Ok, a few...
] systems:
https://www.telnetbbsguide.com/?s=SSH
It was Xibalba, at xibalba.l33t.codes.44510. I actually didn't create an account, so I didn't log in, but it is the initial greeting that gives the warning.
Going to the telnet BBS Guide and searching for SSH shows a number of [Ok, a few...
] systems:https://www.telnetbbsguide.com/?s=SSH