You’ve already applied to college – but now you hope to change your major. Is it possible;? https://insights.collegeconfidential.com/too-late-to-change-college-major
As far as I know the article is accurate. You can ask. What they will say is up to the university or college to decide.
A few schools, such as MIT do not admit by major. MIT decides whether you are admitted without considering your intended major, and then if you are admitted and if you decide to attend will pick your freshman year academic advisor based on your major. If you put a very popular major as your intended major, then you might end up with a freshman year academic advisor in some other area (this did happen to me – my freshman year academic advisor was very good even though in a different field).
One daughter was able to change her major after being admitted but before deciding whether to attend. Both daughters then changed their major during or at the end of their freshman year. This is very common.
I have no experience with anyone changing their major as a way to try to get admitted after being wait listed. I would expect schools to be wary of this practice.
I think that 18 is way too young for a person to know what they want to do for the rest of their career. When my kids went off to university, I lied a bit and gave them a budget that would not have resulted in a catastrophe if a late change in major required a fifth year of university.