Older versions of Catalina can fail to erase the System and Data volumes, but 10.15.6 should be able to, making clean re-installation simpler.
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.
When you go to perform a clean re-install of Catalina, what should you do? Which volume(s) to erase or delete, and how to fix problems?
Don’t rely on being able to use any Apple installer package unless it has been downloaded recently: its certificate is about to expire.
Don’t just hold Command-R and hope that you’ll install the right version of macOS. Here’s structured decision-making to save you time.
You’re running High Sierra, but SystHist reckons you installed Mojave, and have recently applied High Sierra security updates. Isn’t it wrong?
A sequence of steps to safely install the optimum printer driver for new and old models in macOS Mojave.