I think Linux is the most popular of the alternatives listed.

Linux is not a single alternative. It's hundreds if you start digging, and even if you whittle it down to noob-friendly not-completely-idiotic choices, something the proverbial noob are probably incapable of or unwilling to do, there are still like, 5+ decent options to pick from. Asking the proveribal noob to pick from Mint, Ubuntu, Pop, Bazzite, Suse, Debian, Fedora, or any other option is a big ask. There's a lot to take in, especially for someone who just want their computer to work and not dick about with silly bullshit.

It's good that there are options, but most people aren't interested in having a dozen decent choices. They want one, solid, good choice, or at least obvious and clear reasons to pick the different options, and they certainly don't have time to try out everything between heaven and earth, especially for something that needs to Just™ Work™.

How do I download linux

Yep. Top search result was this, amusing: https://learn.microsoft.com/en-us/linux/install

But 2nd was this: https://www.linux.org/pages/download/

It shows 24 distributions, but no newbie guidance. Maybe a wizard UI would help, vs the open-ended "Explore different Linux distributions and find the one that fits your needs"

As your first experience, I think Ubuntu is the easiest. Download it here:

https://ubuntu.com/desktop

Spring for a new hard drive, just in case you hate it with the fires of a thousand suns and need to go back. Then you just swap back to your old hard drive.

I can also recommend Kubuntu if the gnome UI of ubuntu seems too phone-like. If using a laptop where addinga 2nd drive may be too difficult, I have just shrunk the windows partition before running the ubuntu installer.

Looks like from https://github.com/torvalds/linux/archive/refs/heads/master.... but you could also try Ubuntu.