What I meant in my remark about Telnet is that, if you just want is a bidirectional byte pipe to e.g. run a terminal over, then you just need TCP or anything else providing the same abstraction, like TLS-over-TCP or TCP-over-IPsec; whether you then choose to run a getty on that terminal is not for the network to care. (I don’t believe you can get netcat to drive a PTY, so you’ll need e.g. socat. And of course if you want cryptographic authentication then you don’t need or want a getty.)

Telnet, on the other hand, is quite a bit fancier than that and has a fairly involved feature negotiation mechanism for terminal connections that is not entirely in line with the prevalent DEC tradition. As admittedly one of the funkiest examples of what you can do with it, there is for instance a mode[1] where the client is asked to emulate a terminal of the IBM 3270 lineage. (To a practicioner of the aforementioned DEC tradition, those feel like the marsupials of terminals: everything is functionally there, but primitive and derived are occasionally flipped and some features are oddly weak or misdesigned due to a lack of competition.) So if you do actually use Telnet the protocol, by all means, I’ll be delighted to learn what you do with it (partly why I asked in the first place). But if you just need a pipe, then TCP is enough, and netcat or socat make fine ad-hoc clients.

[1] https://tools.ietf.org/html/rfc6270

It’s not so much what I need as what is in common use. Many BBS/terminal stacks for hams haven’t been updated in what seems like decades, except for security updates. It’s tough to get the old guard interested in changing, so they continue to offer their services via Telnet. I’m not sure if what they provide uses any advanced features or not.