How to install macOS Mojave on newer machine

Apple and Silicon. The M1 is here. Great. But since MacBook Pros 2019 the end of old systems and older software is nigh. Unfortunately. Apple seems to care for new sales but not the loyal community of pros and fanboys who want things simply to work out. We paid good money for that.

Therefore I decided to NOT upgrade to a newer machine, getting hot and throttled down i9 MacBook Pro in 2019 but wait and see. M1 came swiftly, your 4000EUR Macbook Pro looks damn old after a few months and investment in a new machine, new OS and new hard and software may be necessary and costly no matter what Apple promises – so it did not get better with Apple breaking the shackles of Intel…

macOS Mojave 10.14.6 is the latest stable release which might make your old software fly, befre you are needing to toss them out of the window. Or invest in a Windows machine, full of RGB lights (yeah!), just to show Apple how upset and desperate you can get…

However, in some cases you may have blocking applications that cannot run, or cannot be upgraded to run on Catalina. Then this workflow can be a ‘last ditch’ solution until you get those ‘blockers’ sorted out. Or you just like the System and do not trust Apple to really bring you innovation or a better design every year – but only more problems and costly software updates. 

We have indeed to get creative…

Important Notice: these instructions will only work for Mac models that can boot to Mojave.

From most of the 2019 machines on, Mojave will also not be supported anymore as to be able to boot from it, and a downgrade has to be at least Catalina. I checked prior if my Macbook Pro 2018 would work…

INSTALLATION PROCESS ON AN EXTERNAL DRIVE

This should be straightforward. Initialize the new external drive (which came formatted as exFAT) and the make it HFS+ (Journaled) or APFS (better if it is an SSD).

First I followed the thread on macrumors https://forums.macrumors.com/threads/macos-10-14-mojave-on-unsupported-macs-thread.2121473/page-731 and got my Mojave Update file SecUpd2020-002Mojave.dmg on 05/2020 from Apple https://support.apple.com/kb/DL2035?viewlocale=en_US&locale=en_U. But this was quite confusing and a long thread, mostly about OLDER machines. I wanted to DOWNGRADE a newer machine (bought and built AFTER the 10.14 was shipped and regularly updated) where there would be new architecture, new graphics hardware, new interfaces. So a lot of kext need to be coming from a newer version of macOS, too.  I found this thread and followed his steps, making a Mojave USB Installer Disk: https://scriptingosx.com/2020/01/downgrading-a-mac-that-shipped-with-catalina-to-mojave/ There are steps to allow external boot and switching off teh T2 chip. But I did NOT erase my data on the external drive, because in this process, I guessed the installation process will erased the data anyway. It didn´t – to my surprise.

DATA MIGRATION

I installed macOS Mojave on an external SSD (Samsung T7 with 1TB) on a APFS Volume connected with Thunderbolt3 for enslaving a Macbook 2018 in that way – and it worked. Stable for a year now, even with Sleep/Awake (most of the time…). The SSD drive had already a system copy made with Carbon Copy Cloner on it, but a lower version of 10.14.5 Mojave – I wanted the last available as an image, like with a normal update. But Apple is not so kind and makes this easy to find…

BUT – normally, this could erase all the data on a drive. New system, clean slate, one might say. To get data over normally one has to entertain the Migration Assistent (in Application > Utilities) to then get all the login info, Wifi, documents, licenses over. No so here. The install resulted in the data intact and all logins working, like carbon copied beforehand. 

It worked, also the external Thunderbolt startup with OPTION – my main system on the internal SSD stays Catalina. Some Apps needed a new machine´s authorization process (Ableton8 e.g.) but the rest was simply sitting there and working. 

Amazing. No migration needed..

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