Asking for an extension is totally fine. Worst case, they say no and that you can’t get an extension and then your deadline remains the same and your back to square 1. So there’s no risk to it, a (good) employer wouldn’t revoke their offer just because the candidate asked for an extension.

Just word the email well and make sure to express your interest in them.

Oct 30 is pushing it a bit in my opinion if the original deadline was next week. I’d say a 2-3 weeks extension is a more reasonable ask. And keep in mind that you can let the other companies know that you have an offer deadline and they’ll accommodate you as long as it’s reasonable (and you do well in the interview of course)