Apple - How can I upgrade to any macOS version that is no longer available in the Apple app store?
As soon as a new Mac OS is released, the previous one becomes unavailable.
The only way to get an older OS directly from Apple is to have previously 'purchased it' - even if it was free - then it will appear in your purchase history in the App Store.
If it's not in your purchase history, then you'll have to get it from a trustworthy friend [or less-trustworthy torrent etc]
10.10.anything will do, as you can still get the combo updater to 10.10.5
It's always wise to get a new OS download, even if you don't intend to install it right now - just so it's always in your history. I have every OS back to Lion in my purchase history - good for if I ever need a disposable OS for testing etc.
As Sierra will not run on older machines, this rule has been relaxed for machines whose last supported OS is El Capitan.
You can download it from here - https://itunes.apple.com/app/os-x-el-capitan/id1147835434?mt=12 - but it will not run if your machine is capable of running Sierra.
If it is capable, then you are back to needing it in your purchase history already.
If you don't have an older version of OSX in your purchase history, another option is to get it from an Apple retail store. Just make an appointment with the Genius Bar, take your computer in (even mac pro/mini/imac), and they can connect an ethernet cable and install any version of OSX from their servers, at least as far back as 10.6. They did if for free when I had it done about 9 months ago, and it was much faster than installing it at home. I believe it only took about 20 minutes.
Some of the previous versions of macOS are linked via support pages they have added to their website. A detailed page that not only lists which versions are available, but also helps users determine which version of macOS they are currently running can be found here: https://support.apple.com/en-us/HT201260
I learned of these when I ran into a similar issue of needing to upgrade Apple hardware after the version I needed was removed from the App Store. Support pages are here:
- Catalina https://support.apple.com/en-us/HT201475
- Mojave: https://support.apple.com/en-us/HT210190
- High Sierra: https://support.apple.com/en-us/HT208969
- Sierra: https://support.apple.com/en-us/HT208202
- El Capitan: https://support.apple.com/en-us/HT206886
- Yosemite: https://support.apple.com/en-us/HT210717
Direct links to download the installer via the App Store or other locations:
- Catalina: https://itunes.apple.com/us/app/macos-catalina/id1466841314?ls=1&mt=12
- Mojave: https://itunes.apple.com/us/app/macos-mojave/id1398502828?ls=1&mt=12
- High Sierra: https://itunes.apple.com/us/app/macos-high-sierra/id1246284741?ls=1&mt=12
- Sierra: https://itunes.apple.com/us/app/macos-sierra/id1127487414?ls=1&mt=12
- El Capitan: https://itunes.apple.com/app/os-x-el-capitan/id1147835434?ls=1&mt=12
- Yosemite: http://updates-http.cdn-apple.com/2019/cert/061-41343-20191023-02465f92-3ab5-4c92-bfe2-b725447a070d/InstallMacOSX.dmg
The details about the hardware that each version supports is listed on each upgrade page.
The most important thing that I'm unsure of is if the App Store links listed in these pages will allow someone to visit those pages and download that version of macOS even if the user hasn't previously downloaded or associated it with their Apple ID. Since I had previously downloaded and associated each of these versions with my Apple ID (with the exception of Mojave), all the App Store download links worked for me.