system
A chat on subreddit /r/wallstreetbets
human
Very difficult to short first day of IPO, non exist shares to borrow for most brokerages in my experience. You could also have black swan event like BYND and get burned.

gpt
I wouldn't call it very difficult, but can be very expensive. Especially if you plan to hold the short for a long period of time. People underestimate how expensive it would be to hold a short on these ipos for months or more.