I don't know about Ubuntu, but while installing Debian it makes it very clear what popularity-contest does and asks the user for explicit consent.

The default option is "I do not wish to participate", so if someone isn't paying attention during the install process and just hits 'Enter', their privacy remains intact.

This, IMO, is the perfect way to do telemetry.

On Ubuntu you still have to explicitly enable it - and unless I missed something in my last couple of Ubuntu installs you are never prompted to enable it during installation. If you want to opt in, you have to do a dpkg-reconfigure and even then the default is still "No".

This is not privacy-hostile in any meaningful way.

Is the hubbub about popularity contest or about the Snap store?

It's about popcon, except for the people who didn't read the article.

The default in Ubuntu is to ask you at install time if you want it installed / enabled or not, for about as long as I remember, and I've been using Ubuntu for since ~5.04ish days.