High Sierra lacks drivers for T2 chips and newer SSDs. It will refuse to install. This OS is strictly for legacy machines (pre-2017).
Sites like archive.org host legacy software. Search for "High Sierra 10.13.6 Installer.dmg". After downloading, : macos high sierra 10136 dmg full
folder, you can create a bootable drive for clean installs or repairs: Plug in a USB drive (16GB+ recommended) and format it as Mac OS Extended (Journaled) and use the following command (replace with your USB's name): High Sierra lacks drivers for T2 chips and newer SSDs
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