I'm trying to figure out what is going on with a Dell Latitude 5480 and an Intel Corporation Wireless 8265 / 8275 (rev 78). The Latitude in question has an SSD with the latest Windows 10 installed and a second SSD with Ubuntu 20.04. The user spends most of his time using the Ubuntu SSD, where he gets expected thruput on any wifi network he connects to. However when he needs Windows, he sees abysmal download and somewhat expected upload. Since this user is semi-clueless with technical problems on his computers. I spent a 20 year career as a sysadmin/"windows janitor" but retired in 2010, so my Windows tech skills have atrophied, but since I'm retired, I've become the defacto neighborhood tech support. If it was up to me, I'd just stay on Linux, but he has some programs he needs to run that do not play well with the Wine windows emulator.
A run with the speedtest website on Windows, on a Starbucks wifi showed less than 1mbps download (this value has been similarly duplicated on other access points) and an upload of 5-6mbps upload, whereas with the Ubuntu SSD installed, 20-30mbps down and similar normal values of upload. I've tried downloading/installing the driver specified by Intel on their website, with no difference, other than Windows deciding the driver on WU was the correct one and reinstalling the WU one. What gives?