How do I get Safari 15 for MacOS 10.13.6?

That’s annoying that they’re actually enforcing it. I tried in a Mojave VM and saw the same redirection to the requirements page, but then I changed “Version/14.1.2” to “Version/15.1.2” in the User Agent and it let me try to log in. I don’t have a login so I couldn’t get any farther, but that might be an option as well.