Choosing the default main stream is only fixed for 1ch or 4ch simultaneous view, from 9ch onwards the default secondary stream is chosen because it is understood that from it will have a lot of load for the system and that the size of the individual channel window will not appreciate the maximum resolution.
In 4ch recorders, if the zero channel is enabled, it loads by default a view that allows to show all 5 at the same time (the 3x3 view), in order to make this configuration you have to disable the zero channel.
In local (keyboard and monitor) the zero channel is disabled in the Live View section, when accessing by web browser the 4-channel view is loaded directly with the main stream selected.
