So what is Plan9's alternative to SSH? SSL seems even worse than SSH in terms of algorithms that you have to negotiate, and thanks to misconfigurations you can end up in a situation with no shared ciphers (if server accepts only RC4 and client rejects RC4 for example).

Maybe tinyssh could qualify as an alternative...

There is cpu for plan9. It's a remoteshell does does mount the local filesystem, so you can continue to work.

I don't think tinyssh is less complex, as it is compatible.

According to that mailing list message cpu uses 9P+ssl, and I consider ssl more complex than ssh. May not be the case on Plan9 as it looks like their ssl only supports old algorithms and not too many of them.