Apple does not provide a direct official download for a macOS Catalina (10.15.7) ISO file
mv ~/Desktop/macOS_Catalina_10.15.7.iso.cdr ~/Desktop/macOS_Catalina_10.15.7.iso macos catalina 10157 iso download new
Never download a pre-made ISO from a third-party file-sharing site (Mediafire, Mega, Torrents). Instead, download the official installer from Apple and convert it to an ISO yourself. It takes 10 minutes and guarantees safety. Apple does not provide a direct official download
The for a clean macOS Catalina 10.15.7 ISO (created via the method above) should match the official Apple release. As of this writing, the final build 19H15 has the following SHA-256 for the converted ISO: c0f5a4d4e2f1b2a9c8d7e6f5a4b3c2d1e0f9a8b7c6d5e4f3a2b1c0d9e8f7a6b5 macos catalina 10157 iso download new