uPnP works fine though? What was the problem you had with it?
For one, monopolies disabling it by default on their equipment? I remember some years ago having to guess the admin password at a vacation house so I could enable UPnP. It's usually framed as a security vulnerability, even.
uPnP fails when multiple devices are fighting over the same port assignments. uPnP fails when people have it disabled, as has been recommended many times over the years.