With ARM-based Macs coming and macOS Crapalina still the most problematic macOS in history, the smart move may be to ASAP get your Mac of choice that can still run macOS Mojave.
Be darn sure to configured Software Update to not “upgrade” to macOS Catalina.
To get your Mojave-ready Mac, here are some choices:
- Refurbished and pre-owned Macs at OWC, such as the iMac and iMac Pro. Availability varies, but ideally I’d recommend a 2019 iMac 5K or an iMac Pro, or a 2018 MacBook Pro in spite of its crappy keyboard (the 2019 MacBook Pro appears to be unable to run Mojave)
- Try to get a 2019 iMac 5K now such as at B&H Photo. See my Mac wishlist at B&H Photo.
It’s not clear to me if Apple has made some firmware change such that ordering a new Mac will be able to go back to macOS Mojave (since it would ship with Catalina)—sorry I don’t have the answer here.
The rumored 2020 iMac 5K probably won’t be able to run macOS Mojave, which means I probably will not buy one, even though I’d love a 4TB or 8TB SSD and a 10-core CPU.
Dave M writes:
Thanks for the many years of advice - I was reading macperformanceguide when I was researching buying my first G5!
Regarding downgrading to Mojave, I bought a refurb 2019 iMac 5k direct from Apple a few months back and then bought 128Gb RAM from OWC for less than Apple wanted for half that amount. My reasoning was that it was the last Mac without a T2 chip, and therefore I will be able to install another OS on it after Apple dropS support for Intel Macs in MacOS.
It came with Crapalina pre-installed, so I spent a day downgrading it, a painful process which included using my 2012 Mac Mini, which is still on High Sierra, to obtain the Mojave installer, then creating a bootable USB stick and wiping Crapalina away.
Unfortunately, the new OS had partitioned the internal SSD into a write-protected Macintosh HD and a writable Macintosh HD - Data volume, which act as one volume under 10.15. Mojave did not update this partition map, treating them as one volume during the install. Now it shows then as separate volumes, and since it can’t handle this setup, Spotlight refuses to index anything, which has clobbered search in Mail, Outlook and Alfred. Still, work to do, and the system worked, so I got on with it.
Eventually I grew tired of having no search, so split the 1tb SSD into two partitions, and used Carbon Copy Cloner to duplicate the Data partition into the new, empty partition. Booting into the Mojave-created partition fixed Spotlight, and there’s been no need to go back to the original.
Just thought I’d let you know about this downgrade gotcha, perhaps you can share it for anyone who takes your advice and buys the 2019 iMac 5K, which is turning out to be a wonderful beast of a machine.
MPG: downgrading is indeed a PITA, but it can be done and once achieved it's good for years, which is the presumed goal—having a stable OS which remains compatible with just about everything that is good for the life of the machine.
Wipe out the internal SSD by booting off an external drive and deleting partitions and erasing.