How I Solved Slow Wifi Connection on Realtek 8812BU USB Adapter

I recently upgraded the WiFi adapter on my PC to a Realtek 8812BU. Setting it up was a breeze, it's plug and play (Windows 10).

However I experienced intermittent speed. 

I use a TP-Link Deco-5 mesh WiFi and was getting quite strong WiFi on my other devices. 

I finally noticed (via Settings/WiFi/Hardware Properties) that the adapter sometimes shifts to a 2.4 GHz band and that's when it slows down.

The simple fix: manually set it to 802.11ac on Device Manager. Then it stays on the 5 GHz band.

Now I'm getting the speed I want!