Are you planning to install this on a device or a stock iOS 15.0 phone?
Getting your hands on specific, older versions of iOS applications—like the (BFI2) IPA you're looking for—usually requires accessing specialized community archives or using legacy tools to pull them from the App Store servers. 1. Check Community Archives
Since this specific file string looks like it belongs to a jailbreak or legacy app community (often associated with the "BFI" or "MTM" archival projects), your best bet is to check repositories that specialize in "undumped" or archived IPAs.