Because I don't want to repeat it every time, I eventually wrote everything down, so know I can just link to it:
For installing Python: "Installing and running Python: the bare minimum you can get away with"
https://www.bitecode.dev/p/installing-python-the-bare-minimu...
To manage deps: "Back to basics with pip and venv":
https://www.bitecode.dev/p/back-to-basics-with-pip-and-venv
And how I justify those very steps: "Why not tell people to "simply" use pyenv, poetry, pipx or anaconda".
https://www.bitecode.dev/p/why-not-tell-people-to-simply-use
At this point it kinda feels like spamming, but honestly, there is too much noise out there, and those points don't come across enough. Especially since most dev are either too little or too much experienced to be helpful.