This is where markdown is fiddly. Two spaces at the end of a line is how markdown can show a line break, but that doesn’t usually work when pumping out info from Airtable into another system. \n I believe is not real markdown. You can read more here : GitHub Flavored Markdown Spec
Use the HTML </br> and see how that works. You can mix in some HTML with markdown however we try and use either straight markdown or straight HTML in our formulas, as mixing can become a bit fiddly.