I'm using Netgear R6220 with OpenWRT (22.03.3). I experienced problems with Wi-Fi where download is "low" - instead of 300+ Mbit/s on stock firmware, download speed with OpenWRT is 180-230 Mbit/s. Wired connection works good and I have my 900/300 internet speed. I'm around 0.5 meter from router testing on iPhone 12 with Speedtest app.
Hi.
Set channel to 36. Lower the power transmit to 20 dBm (25 is atrociously high). Perform transfer test from a computer connected to LAN. Use another computer with AC wifi on the other hand.
I can achieve 40 to 45 MB/s in such case, which is honorable. You should have the same.
Forget about "downloading" something, there are many parameters involved: the server, the transport, routing, wifi. In order to separate, perform transfer from LAN only (no routing, transport). so from a wired computer to a wifi laptop. Are you sure that your laptop connect with AC (wifi5) capabilities?
Another possibility is to reset the wifi config