With Ubuntu 18.04 and latest Firefox it is unreliable, in 2/3 of the cases I get a Timeout and in 1/3 of the cases I'm able to connect. I couldn't find any reason why it works or why It doesn't work. I tried on two different machines. I couldn't find a way that reliably gets a connection. And I do have apparmor working. Trying it was a waste of time.