@sachb
Tried every single item you mentioned in your post except the try channel 149 as I can choose only 36,40,44,48. RESULT is the very same bad speed via 5G wifi so no change - regarding the 149 channel why don't I have it in the router selection list? Firmware? Location?
@GreenBay42
If you can please reread my previous posts for more details but I will try to sumarize all info here
My location: same ISP, same modem, 1Gbit connection
My router DIR-882 is working properly when sending big file from PC (LAN) to Ipad (5G WiFi) - speeds around 550Mbit - SO 5G WiFi is working correctly
My router DIR-882 is working properly when checking internet speed via SPEEDTEST main PC (LAN) - 900> Mbit - so no problem with modem or ISP
My router DIR-882 does not work properly when checking internet speed via SPEEDTEST via any device (Ipad 7th gen, pocophone f1, Iphone 8 Plus, main PC Intel ac wifi 9560) on 5G Wifi every time same exact result 230Mbit no more no less....
My friends location: same ISP, same modem, but 500Mbit connection
My router DIR-882 is working properly when sending big file from PC (LAN) to Ipad (5G WiFi) - speeds around 550Mbit - SO 5G WiFi is working correctly
My router DIR-882 is working properly when checking internet speed via SPEEDTEST via any device (Ipad 7th gen, pocophone f1, Iphone 8 Plus) on 5G Wifi every time around 470Mbit so all OK.
so from this it looks like problem when internet speed from ISP is 1000mbit then WAN to Wifi is bugged as it hard lock internet speed checked via Speedtest to 230Mbit no more no less every single time I try test.
So ISP modem is OK as WAN to LAN on DIR-882 results 900Mbit, yes both locations have same modem/optical converter, yes tried couple of times to reset the modem / optical converter and lastly yes tried all the time same wireless clients.
I am starting to lose my mind.