I do a similar thing myself to exchange currencies. My broker will let me buy a stock in Canadian dollars on the Toronto stock market, and then sell it a few days later in US dollars on the US stock market. And vice versa.

Many Canadian companies trade on both. Shopify is another that you may be more familiar with (though I don’t use that one).

You take some volatility risk over those few days, but on average, you save a lot on fees and make a bit of money over those days. Over enough transactions, even the volatility averages out.