Follow Apple’s instructions for a clean re-install, and you’ll probably hit an error, and be left floundering in Recovery mode with an unbootable system.
Safe mode, installing the Combo updater, re-installing macOS, and other potential solutions to get that update working properly.
How to check whether a macOS Installer app still has a valid signature, and where to find its hidden Installer packages.
Links to official Apple support articles, and important 3rd party pages. How to run Aperture in 10.15, where to get old versions of macOS, and much more.
No more fiddling with contextual menus: this new version also adds a busy spinner, and opens older packages too.
How to check whether any Installer package or app has valid certificates, using this new version of Taccy.
Validating signatures isn’t straightforward. GUI apps are limited, and command tools confusing and prone to user error.
Do you use third-party command tools? Are you using or planning to use Catalina? This explains how 10.15 changes first run checks on those tools, and their effect on all users.
Want to check whether an Installer package has been properly notarized? This new version of Taccy will do it for you.
When you can’t install what the App Store offers: solutions for downloading and installing older versions of macOS for use with Catalina.