This device has 3 WiFi “channels”: 2.4GhZ, 5GHZ-1 and 5GHz-2. This was really confusing at first and the documentation/setup is no help. What I figured out is that 5GHZ-2 is the “backhaul” channel designed for mesh integration of other units. It’s the only one that is AX compatible. That means the 2.4 and other 5GHz will be AC, not AX.

https://www.amazon.com/RT-AX92U-Tri-Band-802-11Ax-Aiprotection-Compatible/dp/B07YD49FZT