I mentioned in my blog post that there is an SSH gateway in between. I tried this on my local system:

  ssh -L 9000:127.0.0.1:8000 user@host

But when I visit http://127.0.0.1:9000/ on my local system, I get a connection reset by peer error. At the same time, in the terminal where I have set up the port forward with the ssh command above, I get this error:

  open failed: unknown channel type

The SSH gateway is forbidding port forwarding as well.

I know we're getting into the weeds here but for the benefit of people learning random things that work slightly differently (tm)

A possible workaround for this specific scenario would be to use 'sshutle' which runs a python script on the remote end to terminate the traffic.

Except in your specific scenario you'd have to somehow trick it to execute using a login shell like one of the other comments shows.

Having said all of that, I would just do what you did :)

I think we can assume that if they are restricting things as the article describes they also disabled port forwarding.

That's right. See https://news.ycombinator.com/item?id=24507146 for example.

Port forwarding your local machine is always an option.

Or you can open SSH back to your local port forwarded server from the remote SSH shell. At that point you can pipe whatever you want to/from your local server using the standard SSH commands.