As an aside, I’ve noticed that ChatGPT uses em dashes (“—”) quite frequently — much more often than I’m used to seeing on the web. It’s a bit surprising, considering it's largely trained on web-based data.
You probably won't encounter it in professional(-ish) writing very often (since that's premeditated and usually written on a computer, and most computer users are still on Windows), but in more informal situations (microblogs, text chat) most people don't really care as much to correct the behavior and nobody turns it off, meaning that the frequency of em dashes is unintentionally way higher than it probably should be.
Punctuation is usually set closed on at least one, if not both, sides, though there are exceptions.
(Lots of people use en-dashes set open instead of em-dashes set closed for the uses for which they are interchangeable as a matter of stylistic preference, though.)
[0] https://chatgpt.com/share/6836f23d-9b58-800b-8cea-0a86a58076...