WiFi only 150 kbit/s with GL-MT300N-V2 3.203

WiFi is slow even after a fresh 3.203-0908 firmware upload.

Install 3.203-0908, connect to Mango WiFi, go to 192.168.8.1.
Already the first page - asking to set language - is slow.

I just wrote I try to use 3.203-0908 and not the released 3.203-0805 because I need WDS.