Renergen General Discussion, page-3440

"Some rocket launches have experimented with gases such as argon and nitrogen, which are also inert and can sometimes be cheaper. Helium, however, is much more prevalent in the industry."

"Back on Earth, SpaceX's Polaris Dawn mission has been delayed because of helium issues on ground equipment."

So SpaceX use it on ground equipment I guess plus if and wherever else on the actual rockets

https://www.reuters.com/science/what-is-helium-why-is-it-used-rockets-2024-09-07/#:~:text=Back%20on%20Earth%2C%20SpaceX's%20Polaris,Mexico%20desert%20late%20on%20Friday.