According to the author, the current version at 46e4bfab of
redox-ssh is in a generally working state with working encryption using the implemented ciphers.
There are a few undesireable workarounds, because cloning of a TcpStream did not work. Using the newer Redox stack, this should work better.
Another place needing attention is the sub-process management where the shell runs. Back then Redox did not support asynchronous IO. The situation has probably improved in the meantime.