@dkiwi    @ZetolFox 

Hello, thank you both for reporting the speed issue you encountered with the AX50, please help verify some details, and we will try to fix it together:
1. Without any other devices connected when the speed on the computer drops significantly, please connect one computer to the AX50 directly and go to speedtest to run the test for 3 times and show us the screenshots of the test results.
And please tell me the wired link speed at that time, how to get that? You can refer to the below link.
https://www.tp-link.com/faq-2265.html
2. What is the speed tested on the Tether app? It might be different from that on your computer, we may think the Tether speed is more like the connection speed between the router and your internet, which would be different from the speed you can get on the computer, while we can verify it first.
3. Do you enable any QoS setting on the router? Kindly show me the QoS setting page on your AX50, try to disable it then check again. On the Tether Homecare page-QoS, check and ensure it is on the Standard Mode, then get back to the Clients' page, check all the clients connected to the router and ensure the High Priority is disabled.
4. If the wired connection speed from the AX50 is good, try a mobile app to analyze the surrounding Wi-Fi, review all the channels in 2.4GHz and 5GHz. Next, review the channels on the router for 2.4GHz and 5GHz. If the channels match that around you, an indication of overcrowded. Manually adjust the channels for 2.4GHz and 5GHz to lesser use channels.
5. Ensure the firmware of the AX50 is up-to-date, and there are possibly other wireless parameters that need tweaking, such as Power Transmit, narrow or wide band, etc. but start with the above and below link:
https://community.tp-link.com/en/home/forum/topic/200588

@dkiwi 

Hi, thanks for getting back.

May I know what is the bandwidth provided by your ISP? Do you mean you never get more than 220Mbps on the iPhones? As suggested, please ensure the QoS is disabled on the AX50, this can only be modified on the Tether Homecare page-QoS, check and ensure it is on the Standard Mode, then get back to the Clients' page, check all the clients connected to the router and ensure the High Priority is disabled.

Meanwhile, what is the OS version of these iPhones, are they iOS 14.0.1? How about the link speed when they connected to the 5GHz network? Can I have a screenshot?

@dkiwi 

Hello, thanks a lot for all the detailed info.

We would like to escalate your case to our engineers, and they will help follow it up, if you are willing to do further analysis, please check your inbox and respond.    

Good day.