GNU/Linux Debian Buster TP-Link TL-WN821N V5/V6 Wifi Driver Setup – Step-by-step Guide
How to Install TP-Link TL-WN821N V5/V6 Wireless 802.11ac Driver on Debian Buster 10.x GNU/Linux – Step by step Tutorial.
And the Debian Buster TP-Link TL-WN821N V5/V6 Adapter is based on the Realtek rtl8192EU Chipset.
So here below you find instructions to Install rtl8192EU Driver on Linux.
Especially relevant, if you are Unsure about your Wifi Device Chipset then see: How to Get Wireless Adapter Info on GNU/Linux.

GNU/Linux Debian TP-Link TL-WN821N V5-V6 Wireless Driver Installation Guide