Tablet and Wi-Fi AP can't agree on a channel. Which device is violating the 802.11n standard?

Yesterday I received a Fire 7 (9th Gen) Tablet. According to the official datasheet, it supports dual-band 802.11n Wi-Fi. To my surprise, the SSID of my 5GHz Wi-Fi router didn't show up. After talking to support it was explained to me that the device only supports the channels 36, 40, 44, 48 on the 5GHz band. At the same moment, my router doesn’t allow me to specify the channel it is using.

So I talked to both support staff for the tablet and the router. The ISP who is the provider of my router is stated:

It's the tablet's fault it should be able to scan on all channels. Other devices can connect on the 5GHz band without problems.

The Amazon support, on the other hand, stated:

It’s the router's fault, it should be able to specify the channel it is using. The tablet can connect to other 5GHz Wi-Fis without problems.

So my question is: Which device violates the 802.11n protocol standards? Or is it totally valid that two devices which both support 802.11n on the 5GHz band aren’t able to connect?

Who is violating the 802.11n WiFi standard?

Nobody. They just chose not to bother with all the complex regulations surrounding radio use. So they only support a subset of the available channels.

5 GHz channels 36, 40, 44 and 48 are the only channels that can be used without radar detection, power control etc, indoors, world-wide (well, almost). Many early 11ac(-ish) routers don’t support other channels at all, due to driver and hardware limitations.

From searching the net, it appears all sorts of Amazon devices have a long history of only supporting these channels for 5 GHz Wi-Fi. There is nothing you can do about that. It is also not unusual at all, unfortunately.

Unless you want to use large amounts of data, just use 2.4 GHz Wi-Fi. It has vastly superior range anyway.

If you do want to use 5 GHz Wi-Fi, you need a different/additional router/access point.

I'll say it's probably neither. Both of them being cheap crap doesn't necessitate either of them violating any standards.

As far as I know the 802.11 standards neither require a device to support all possible channels, nor that the selection of channel can be made by the user.

Personally I would blame the router, as it's too lame that it provides no means for the user to fix the selection of channel to one that can be used without DFS, while I think it's tolerable that a client device supports only those channels.