Gl-x750v2 with USB Wifi AWUS036ACHM

Okay, looks good so far. I’ve hat iwconfig in my mind, that’s why I was somewhat confused at the beginning.
Only 54 Mbps? Is is a BG only stick?

Could you give is the output of the command iw dev? (or iwconfig, but I will be too lazy to read it all).

I expect something like:

root@GL-AXT1800:~# iw dev
phy#1
	Interface wlan1
		ifindex 11
		wdev 0x100000002
		addr 00:03:7f:xx:xx:xx
		ssid GL-AXT1800-xxx
		type AP
		channel 6 (2437 MHz), width: 20 MHz, center1: 2437 MHz
		txpower 20.00 dBm

And in the next step we could try to assign it.

The page ‘Network - Interfaces - Tab: Devices’ says for the option ‘Bridge ports’:

Specifies the wired ports to attach to this bridge. In order to attach wireless networks, choose the associated interface as network in the wireless settings.

In ‘Network - Wireless’ with the Button [Edit] at the device, at ‘Interface Configuration’ I can see the Option ‘Network’, with the value ‘LAN’ …

I do tink this is what you are searching, But I don’t have a USB WLAN device with me and checked it on the AXT-1800 (Slate AX) with Firmware 4.0.2 (Kernel 5.4) … So it could be somewhat different at your device.