What is the "Internet box"??
I mean the router that comes with the modem my ISP provides. The router,
named Pace v5471, runs free software: https://github.com/alacn1/pace_v5471
It is surprising that Firefox properly renders the page but not Abrowser,
which is a derivative. I use the router in my Internet box and Abrowser
properly renders its Web configuration interface.
The Web page to configure the router is probably badly formatted (invalid
HTML or CSS): Firefox manages to bypass the issues, unlike some other
browsers. Sadly, many Web developers only care that Chrome, Edge/IE, Firefox
and Safari properly display the page... if not only Chrome.
I would try to do what the guide says: click on what is supposed to be a
drop-down menu, type tun0 and [Enter]. If that works, it is a terrible
graphical interface: it should not be a drop-down menu, as you wrote.
It is supposed to open something and I should be able to choose tun0.
Te guide you link to does not say that. It says:
type "tun0" at "Custom Interface" and press Enter
