Linux repo init not working

I am working on a Windows laptop with WSL2 running Ubuntu 20.04 LTS. I installed the “Required Packages for the Build Host”. I try to follow the setup for building a Linux OS on your page Build a Reference Image with Yocto Project.
I managed to install repo as suggested:

$  mkdir ~/bin
$  export PATH=~/bin:$PATH
$  curl > ~/bin/repo
$  chmod a+x ~/bin/repo

Now, I am stuck with the “First-time Configuration” as suggested:

$ mkdir ${HOME}/oe-core
$ cd ${HOME}/oe-core
$ repo init -u -b dunfell-5.x.y -m tdxref/default.xml
$ repo sync

The (modified) command

$ repo init -u -b dunfell-5.0.0 -m tdxref/default.xml

returns the error message

/usr/bin/env: ‘python’: No such file or directory

I think python is installed, it is version 3. The command python3 shows:

Python 3.8.5 (default, Jul 28 2020, 12:59:40)
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.

How can I get the repo init command running?

Maybe just sticking to some sane development environment would help?