I bought USB wifi adapter Realtek Semiconductor Corp. USB3.0 802.11ac 1200M Adapter and connected it successfully on Ubuntu and Debian.
Following worked on Ubuntu 20.04.6 LTS
lsusb
sudo apt update
sudo apt install linux-generic
iwconfig
#nm-connection-editor
#nmcli connection up [YourWiFiConnectionName]
sudo apt update
sudo apt install linux-generic
iwconfig
#nm-connection-editor
#nmcli connection up [YourWiFiConnectionName]
Debian (Proxmox)
lsusb
# 0bda:b812 Realtek Semiconductor Corp. RTL88x2bu [AC1200 Techkey]
apt update
apt install wireless-tools
iwconfig
apt upgrade
apt install pve-headers-$(uname -r)
apt install pve-firmware
reboot
iwconfig
# 0bda:b812 Realtek Semiconductor Corp. RTL88x2bu [AC1200 Techkey]
apt update
apt install wireless-tools
iwconfig
apt upgrade
apt install pve-headers-$(uname -r)
apt install pve-firmware
reboot
iwconfig
