To buy Shopify stock on US or UK exchange for diversification purposes?

Looking at adding some Shopify stock to my portfolio. I'm keen to not invest in more US domiciled stocks since I already own a bunch and diversification is important. My trading platform (CMC Markets) allows me to purchase Shopify stock on the UK stock market but in US dollars… Would it be beneficial from a diversification perspective to purchase the stock on the UK exchange? Also does the fact that the UK Shopify stock costs US dollars mean that the stock is still somehow domiciled in the US anyway?

Thanks in advance!