Now that the first step is solved other problems comes out
The gui from the web doesn’t work properly while the gui from the lan is ok
In the gui I have access from the web at the upper left corner near syncthing logo I read “(unknown)” while in yhe gui from lan I read correctly “ubuntu”
Other problem is that in the gui from web I read listerners “0/” while in the gui from lan I read listeners “3/3”
The third problem is that in the gui from web the menù doesn’t work…If I click settings no settings popup appears. The lan Gui menù works properly.
It probably doesn’t like it not being accessed from localhost.
What you are doing is fairly dangerous. You are running syncthing as root and making it’s ui accessed via the internet. By default it runs without https, so your UI password can be intercepted, and then it’s fairly trivial just to take over the whole machine.