in Proxmox Host:

apt update
apt install pve-headers

nano /etc/apt/sources.list

deb http://deb.debian.org/debian buster-backports main

Save.

apt update
apt install -t buster-backports wireguard-dkms

modprobe wireguard
echo "wireguard" >> /etc/modules-load.d/modules.conf

In LXC Container:

apt install wireguard

or use piVPN

curl -L https://install.pivpn.io | bash