The go ssh packages are a popular choice:

https://github.com/shazow/ssh-chat

https://github.com/zachlatta/sshtron

https://github.com/quackduck/devzat

https://github.com/donuts-are-good/shhhbb/

There's also a assembly library:

https://2ton.com.au/sshtalk/

And for rust there's trush, and for python paramiko as mentioned.

> expose a TUI/cli-app over ssh without actually caring about securing OpenSSH

If you already have an app, see maybe:

https://drewdevault.com/2019/09/02/Interactive-SSH-programs....