I have had this issue ever since I rebuilt my desktop using an ASUS PRIME B450M-A/CSM mother board .
In a nutshell my Panda Wireless PAU06 wifi usb stick (2.4 GHZ) runs very slowly . When plugged into a USB2 port it might do 10Mb/second .
The same device when plugged into a USB2 port on a 7+ year old dell laptop running the same version of KDE Neon will do 60+ Mb/second connected to the same ssid on the router (2.4 GHZ)
I have been through the ASUS BIOS but have never found any setting that helps (there are not many settings) .
I also have a pci wireless card that runs 70+ Mb/second connected to the same ssid on the router (2.4 GHZ) .

It seems as though there is some issue with the Linux drivers and the ASUS mb usb .

Any thoughts ?

Operating System: KDE neon 5.21
KDE Plasma Version: 5.21.4
KDE Frameworks Version: 5.80.0
Qt Version: 5.15.2
Kernel Version: 5.4.0-70-generic
OS Type: 64-bit
Graphics Platform: X11
Processors: 8 × AMD Ryzen 5 2400G with Radeon Vega Graphics
Memory: 15.4 GiB of RAM
Graphics Processor: AMD RAVEN