Instructions to setup s3cmd in Debian derivatives might need to be updated

Following the instructions for Debian derivatives here: https://docs.csc.fi/data/Allas/using_allas/s3_client/#getting-started-with-s3cmd

Encountering the following error on Ubuntu 24.04.02:
```
ubuntu@pipeline-vm:~$ sudo pip3 install python-openstackclient
error: externally-managed-environment

× This environment is externally managed
╰─> To install Python packages system-wide, try apt install
python3-xyz, where xyz is the package you are trying to
install.

If you wish to install a non-Debian-packaged Python package,
create a virtual environment using python3 -m venv path/to/venv.
Then use path/to/venv/bin/python and path/to/venv/bin/pip. Make
sure you have python3-full installed.

If you wish to install a non-Debian packaged Python application,
it may be easiest to use pipx install xyz, which will manage a
virtual environment for you. Make sure you have pipx installed.

See /usr/share/doc/python3.12/README.venv for more information.

note: If you believe this is a mistake, please contact your Python installation or OS distribution provider. You can override this, at the risk of breaking your Python installation or OS, by passing --break-system-packages.
hint: See PEP 668 for the detailed specification.
```

Start with the linked “Getting started with s3cmd” documentation page and reproduce the `sudo pip3 install python-openstackclient` command on Ubuntu 24.04.02. Confirm an installation approach that works with Debian derivatives and update the instructions so they no longer produce the reported externally managed environment error.

Written by the indexing model from the issue text.