The particular bet I linked to is probably a bad idea though, because there is a causal link between OpenAI doing well and deciding to go public. So this is not the way to bet on it crashing and burning.
Betting on the trainwreck is quite easy, you got nothing to lose in the analogy, while shorting companies will cost you something, most times a lot if the bet has the wrong timing.
If OpenAI is worth $5B, 4% of MSFT market Cap is Open AI.
ARK Venture Fund (ARKVX) holding is 7.2% of its total but also has xAI, Anthropic and lots of other AI
https://www.ark-funds.com/funds/arkvx#hold
OpenAI going bust might be a shock to shareprices of publicly traded companies like Oracle, CoreWeave, Softbank and the like
EDIT: obviously if OpenAI is worth $500B, not 5