The email sim doesn't allow booking but should still work to demo functionality. And it's not geo-limited. What are you seeing?
Airlines also tend to present different prices for different locations/currencies so I doubt this would be as simple as a UI change (though that would still go a long way!).
Beyond the price differences, airlines also grant scoped 'ticketing authority' in jurisdictions (eg. can only sell these tickets in EU or US+Canada etc).
Frame 6: You guys are buying tickets without a vpn?
I kept trying to do flights from Adelaide (A capital city, but a smaller) to Sydney and back.
It couldn't find anything.