The problem has been solved. Archer is healthy, though. The issue stemmed from the ONT device from the provider. Despite replacing it with a new Dasan H665 model, the Wi-Fi speed was still reduced by...

If I set mode to "Only AX" - NetSpot show this connection mode as "ac/ax". Why?

I have an AX11000 V1 router and a 600/60 mbps fiber optic connection. The device from the fiber optic (Dasan H665) is connected to the router with a Cat 7 cable. For over two years, everything worked...