Does anyone know where I can download the installer for High Sierra? I want to upgrade a 2013 iMac from Sierra so I can use Omnifocus 3 and I think installing Mojave might grind it to a complete halt.
As far as I know, at the release of Mojave, the High Sierra installer is no longer available. If you need it, you need to get in touch with someone who already have it downloaded.
Might be possible to get it from Apple – go to the Genius Bar. However the Combo updater on that web page might work.
Not that it helps you, but Apple used to keep the macOS upgrades in the App Store but stopped (I think with Sierra). I never trusted the App Store so always kept the downloads in an archive. Maybe there is someone near you that has done the same and would put it on a USB flash drive for you.
I actually downloaded the installer pre-Mojave (as it’s the last OS my mid-2011 iMac is approved for) but still haven’t installed it. I’d be happy to share - if that’s a thing. My inner pragmatist is content with El Cap because “if it ain’t broke…” and all that - the software I use runs just fine, so far. I assume I’ll eventually have to install though.