How to load website from macOS as if using iOS for this particular website in safari

I've been trying to figure this out for a while. Here's the answer:

Chrome has a flash player built into it, and it updates automatically. Other browsers use an external flash player. If you're like me, you have flash player installed outside of chrome for other browsers. Chrome doesn't seem to handle this very on it's own, but you can disable one or the other by going "about://plugins" in chrome, expanding the details (+ details at the top right), and finding the flash section and clicking disable on one or the other.

It doesn't seem to matter too much which one you use, but turning one off dramatically improves flash performance and overall memory usage for me.

Here’s a two-year-old topic on Quora asking the same question. No answer yet.

This leads me to believe there is a way to do what you want. Always changing the UA string using the menu is annoying, but at least it works.

The Opera web browser has a feature that does what you want. But of course, if you have to install a separate browser anyway, you may just as well install Firefox 3.6 and use that to access the site you’re talking about.