I have an 2 yr old Inspiron 7573 2-in-1 that, of course, just went out of warranty. I had Xfinity 200Mbps Blast and was doing just fine, consistently getting 200+ on WIFI at the laptop. I upgraded to 400Mbps because, for whatever reason, a new deal offer doubled my speed for less money than I was paying for 200Mbps. Although promised smooth transition "at midnight", that never happened and I contacted Customer Service. They instructed to unplug / re-plug modem to "install" the upgrade. The net effect of that maneuver was to immediately wipe out my 200+ Mbps WIFI speed at the laptop to < 10 Mbps. Comcast immediately denied they caused that to happen. Tech came to the house next day, upgraded Modem from XB3 to XB6 and got 400+ Mbps flowing, but the laptop only got that number from an ethernet connection. Laptop WIFI clocked under 100 Mbps even when laptop was in the same room as the modem. (FYI: Tech's phone picked up WIFI everywhere in the house at 400+.) Tech also took no Comcast responsibility for my WIFI crash and concluded "your WIFI card went bad, it happens." Contacted Dell Support who said it was a software issue and wanted $99 to provide what they said was the solution I needed. So, being a skeptic and a cheapskate, I was now on my own again. I ran Dell Diagnostics (everything passed) and downloaded all available updated Drivers. WIFI improved to 100-120 Mbps, but nowhere near what it should be. I also found these two and downloaded them as well.

12/12/20  driver downloaded and installed successfully Hide drivers 

•  Intel 3165/7265/8260/8265 WiFi driver Intel-3165-7265-8260-8265-WiFi-driver_120C3_WIN_21.40.1.2307_A08_03.EXE (156 MB) View details
•  Intel Dynamic Platform and Thermal Framework Driver Intel-Dynamic-Platform-and-Thermal-Framework_74P16_WIN_8.3.10209.6897_A12.EXE (14 MB) View details

Anybody have any idea what my core problem is and how to fix it?

Staying connected to ethernet by running a cable room-to-room kinda defeats the purpose of having WIFI.

Any thoughts and/or specific help would be much appreciated.......thanx.