5 hubs deep and 127 devices per usb controller (not port)

To confuse this more many usb3 or newer controllers won’t handle more than 32 devices.

Now add to that most 7 port usb hubs are actually 2x 4 port hubs.

You may be starting to see why it is so hard to definitively say if a certain usb setup will work or not without testing the actual hardware.

Side note, a lot of usb devices even count as 2 devices due to hw encryption chips, like wd external hard drives.