I have poor wireless speed 200 mbit on 1000mbit line...

[Gijsy123]

I am having this same issue on my orbi rkb353.

I have poor wireless speed 200 mbit on 1000mbit line...

The speedtest in de orbi app says that de orbi router has 980mbit download en 946 mbit upload so thats good on that side.

5Ghz is indeed greyed out and is stuck on 108 dfs chanel. 

Did you solve the problem on your orbi system or are you still having the issue?

[FURRYe38]

What Firmware version is currently loaded?
What is the Mfr and model# of the Internet Service Providers modem/ONT the NG router is connected too?

What wifi devices do you have and speed testing with. Some devices on 5Ghz top out or max out at around 200-500Mpbs and will never see anywhere near 900-1000Mpbs due to there 2x2 MIMO design and support. 

What is the size of your home? Sq Ft?
What is the distance between the router and 📡 satellite(s)? 30 feet or more is recommended in between RBR and RBS🛰️ to begin with depending upon building materials when wirelessly connected.

You can't change the 5Ghz channel on the RBR? What browser are you using? Try a different browser? 

What channels are you using? Auto? Try Auto and 48 on 5Ghz. Or try setting manual channel 1, 6 or 11 on 2.4Ghz and 40 to 48 channel on 5Ghz.
Any Wifi Neighbors near by? If so, how many?

Try disabling the following and see:
Armor, SPC, Traffic Meter.