Delete the installer and redownload using the official App Store link. Or in Terminal, run sudo spctl --master-disable before launching the installer.
When you open an old 32-bit app, Catalina will show: “The application X needs to be updated.” There is no workaround. You must find a 64-bit replacement or keep High Sierra in a separate partition. how to update macos high sierra 10.13.6 to 10.15
There are two methods to upgrade to macOS 10.15: using the App Store and using a bootable installer. We'll cover both methods: Delete the installer and redownload using the official
Your drive has a read-only snapshot that conflicts. Fix: Restart, hold Cmd + R to enter Recovery Mode. Open Disk Utility → First Aid on your main drive. Then try the installer again. If that fails, you may need to erase the drive (from backup) – last resort. You must find a 64-bit replacement or keep