Is there any way, how to check internet speed coming directly to the router? Because I am getting unstable speeds on my desktop. But stable, while I connect the main cabel directly to my PC. So I’d like to see what exact speed is the modem receiving.

I have an optic internet cable connection of 1 gbps.

Main cabel from provider -> PC = all the time 900-920 mbps (up and down)

Main cabel -> AX 90 ->  PC = sometimes 600 mbps, sometimes 800 mbps (results jumps here and there)

All on cables, no wifi.

All testing is done via speedtest.com. I did factory reset and updated the latest firmware on the router.