Absolutely. Just keep it off the internet or behind a strict firewall. Final tip If the installer refuses to run because of an expired certificate, set your Mac’s date back to 2019 before launching the installer:
sudo date 0101010119 Run the installer, then reboot and fix the date. Have an old Mac you’re keeping alive with High Sierra? Drop a comment below—I’d love to hear your story. macos high sierra dmg
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyUSB (Replace MyUSB with your USB drive’s name.) For daily use? No. It no longer receives security updates. Browsers like Chrome and Firefox have dropped support. Absolutely