Support Us payment page makes it hard to pay with alternate browsers

I wanted to pay to use the Dark Reader extension because it's great! Unfortunately the payment option isn't available if viewing the site in a browser other than Chrome or Firefox (see screenshot). I was able to set my user agent to either of those two to get the payment option to appear.

I'm using Orion, but I also tried this in Safari on macOS, and doing it that way enabled me to pay with Apple Pay!

I suspect this is intended to keep people from paying for the extension and then being disappointed it doesn't work in their unsupported browser. But I wonder if instead, a better option would be a warning about unsupported browsers that appears for those users? I almost thought the payment option had been removed and the project wasn't accepting payments any longer.