The convention
That's one convention. I don't like it, I prefer to keep my venvs elsewhere. One reason is that it makes it simpler to maintain multiple venvs for a single project, using a different Python version for each, if I ever want to. It shouldn't matter to anyone else, as it's my environment, not some aspect of the shared repo. If I ever needed it there for some reason, I could always ln -s $VIRTUAL_ENV .venv.
Learn pyenv
I have used pyenv. It's fine. These days I use mise instead, which I prefer. But neither of them dictate how I create and store venvs.
Shell scripts within Python packages is depreciated
I don't understand if what you're referencing relates to my comment.
Thanks, yes, I use nox and github actions for automated environments and testing in my own projects, and tox instead of nox when it's someone else's project. But for ad hoc, local and interactive multiple environments, I don't.