Install Docker and Portainer inside Debian LXC inside Proxmox

Start with a base Debian server, then update sources repository:
apt-get update

Installing pre-requisites:
apt-get install ca-certificates
apt-get install curl
apt-get install gnupg
apt-get install lsb-release

Get the official Docker GPG key:
curl -fsSL https://download.docker.com/linux/debian/gpg | gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg

Add the Docker Repository to the sources.list.d directory:

echo \

  "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/debian \

  $(lsb_release -cs) stable" | tee /etc/apt/sources.list.d/docker.list > /dev/null

apt-get update

Install Docker Engine:

apt-get install docker-ce docker-ce-cli

apt-get install containerd.io

Install Portainer:
apt-get install docker.io

Enable (as part of start-up sequence) and Start Docker:
systemctl enable docker

systemctl start docker
systemctl status docker

Download, Install and Run Portainer:
docker run -d \
--name="portainer" \
--restart on-failure \
-p 9000:9000 \
-p 8000:8000 \
-v /var/run/docker.sock:/var/run/docker.sock \
-v portainer_data:/data \
portainer/portainer-ce:latest