For the developers out there following the development of Podman you will know that there is no one line command available to install Podman on Ubuntu 20.04.

However its very easy to install with the following procedure:

curl -L "https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/xUbuntu_20.04/Release.key" | sudo apt-key add -

echo "deb https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/xUbuntu_20.04/ /" | sudo tee /etc/apt/sources.list.d/devel:kubic:libcontainers:stable.list

apt-get upgrade

apt-get install podman

You may use the same procedure also to install Podman on the default Ubuntu 20.04 installation of WSL2 (Windows Subsystem for Linux)

As for the versions of Ubuntu newer than 20.04 your should be able to install Podman directly using the standard command:

apt-get install podman