I have very recently purchased the AX6600 GX90 and downloaded the Tether App. For the most part, it works well. I have noticed that there are differences between the GX90 browser GUI and Tether App in terms of available icons. On the browser GUI, there appears to be no option to change icons to suit various applications, however, on the Tether App, icons are available. I have tried to change the icon applicable to my printer and although I can assign an icon, it will not save it. I'm assuming that this is a firmware issue on the GX90 or the Tether App is not completely compatible with the GX90 router. Either way, going forward, it would be nice if the situation was resolved.
Tether App AX6600 GX90