PROBLEMS WITH 2.4 GHZ WITH RBR50

Yes, Netgear appears to have locked the Region Code of units sold in North America and the user cannot change it. We can only speculate what the reason may be. The end result is that the system will follow the North American WiFi standards:
* 2.4G channels 1-11. (12 and 13 will not be used)
* 5G channels appears to be the same in Brazil as in the US.
https://en.wikipedia.org/wiki/List_of_WLAN_channels#5_GHz_(802.11a/h/j/n/ac/ax) 
This is annoying, but probably not fatal.

The issue with Internet of Things (IoT) devices proclaiming (in BIG, BOLD type) "Must have 2.4G WiFi" can be an issue, but 95% of the time is not an issue.

It is entirely correct that a customer WiFi system with NO 2.4G WiFi will be unable to support these devices. This is similar to a flashlight saying, "Requires (2) AA batteries." If you have a drawer full of C cells, D cells, 9-volt, and AAA batteries, but ZERO AA batteries, then the flashlight will not work.  All modern WiFi systems provide 2.4G WiFi.  The warning is needlessly alarming.

IoT devices cannot detect 5G WiFi, just as they cannot detect FM radio or television signals.

There ARE some specific IoT devices which have poorly written smartphone applications.

The concensus on the forum is this:

TRY IT FIRST. Do not create a problem where there is not a problem. Follow the setup instructions and simply ignore any warnings about "2.4G WiFi".

If some specific device cannot be set up, double check with the manufacturer support information or post on this forum about it.

As a LAST RESORT, turn off the Orbi and create a temporary WiFi network at 2.4G with EXACTLY the same WiFi SSID & password.
* Dig out an old, inexpensive WiFi router that you keep for just this purpose. (I have two.)
* Create a WiFi Hot Spot on a smartphone with these credentials.

Go through the setup process.

Once the IoT device can connect, then power everything off, turn the Orbi back on, and power up the IoT device. It will connect immediately.

Hope this helps.