I'm trying to get a bootable hard drive with macOS Sierra going so that I can use Octane Render. My Macbook is running macOS High Sierra, which is apparently buggy with Octane at the moment.
I purchsed a WD easystore, partitioned it to be Mac OS Extended (Journaled), and put the macOS Sierra installer on it (I downloaded this from the App Store). First, I was starting up with that disk and continuously getting the following error message: "This copy of the Install macOS Sierra.app application is damaged, and can't be used to install macOS."
NOW I'm not even getting to that stage, the drive isn't even showing up as a bootable disk! When I go to System Preferences > Startup Disk, it's not even there as an option.
Please help me - getting verrrry frustrated as I have no idea what I'm doing. Thanks in advance!