The only supported OS is Ubuntu 18.04 LTS, which comes preinstalled with python 2.7 and 3.6. Not arguing that there are situations where a simple bash script is way better than an additional tool with dependencies

Which OS comes without Python pre-installed? But I agree, the less is installed the better.

Alpine Linux, Busybox, ArchLinux are examples.

Alpine Linux doesn't have bash installed by Default either. Don't know about the others

ArchLinux - wrong, has python preinstalled even if you go with the base image. Alpine - doesn't even contain bash in the miniroot edition Busybox - similar to Alpine

If python happens to disappear from all linux distros ansible can still work with the raw module.

In any case, the bash script posted is based on apt install so it's not going to work on much less amount of distros rather than if it was just an ansible role.

Windows?

Windows doesn't come with bash by default either ;)

Python is extremely easy to setup on Windows though.

Time have changed a lot though as you can now run complex bash scripts on the Windows Subsystem for Linux (published by Microsoft).

Windows Subsystem for Linux https://docs.microsoft.com/en-us/windows/wsl/about

Print Screens and Doc of running as Bash Script on Windows: https://fastsitephp.com/en/documents/file-encryption-windows

Which can be resolved by running SCCM

In a history of running ansible for ages against 5k-25k machines regularly in not a single case I had to install python on any one of those before running a playbook. There's a reason why it's described as agentless.

In fairness, there are some dependencies depending on what you're doing; ansible's use of apt needs python-apt (or maybe aptitude?), and I have hit that one hard (granted, on termux, which is a weird target). Oh, and I had to do the equivalent on Fedora. Which is fine, mind, just pointing out that dependencies do still happen in ansible.