Installation of macOS
New Macs
New Macs come with macOS pre-installed.
Reinstallation
To re-install macOS follow the instructions from https://support.apple.com/en-us/HT204904.
Updates
It is the users reposibility to ensure to always run a supported version of macOS.
Reminders
As of July 2022 Macs that are enrolled in the Mac Self Service that run an outdated major version of macOS (currently anything lower than 10.15) will receive a monthly reminder that their macOS is unsupported.