apple tv

You can find macOS upgrades in the Mac App Store, which itself is an app on your Mac.

How to upgrade to macOS High Sierra - Apple Support

I don’t recall the exact details of the functionality of Safari on Yosemite, but I think there is a checkbox in the menus somewhere to stop/allow pop-up windows, and there may be extensions in Preferences that can be turned off and on. If you have the sprockets icon in the browser window toolbar, then that may be a shortcut to disable content blockers that follow the built-in standard, although I would expect that this shouldn’t interfere with Apple’s own sites.

The site uses an iframe (nested content from another site/subdomain) for the sign-in window. There is a slight delay for me (<2 secs). Disable any content blockers or browser add-ons that may block the needed cross-site connections (or allow those connections for Apple’s sites as exception).

A 2011 Mac Mini can be software upgraded to macOS High Sierra 10.13, but not any further. Not macOS Catalina 10.15.

The Apple TV app would be installed if your Mac supports upgrading to MacOS Catalina. If not, you can access Apple tv Plus on a browser @  tv.apple.com