OS Upgrade

You can upgrade to Big Sur and possibly Monterey.macOS Big Sur is compatible with these computers - Apple Support (PH) For Monterey. macOS Monterey is compatible with these computers - Apple Support Go to the App Store for Monterey.How to get old versions of macOS - Apple Support If your going to go to Big Sur or Monterey Start with Mojave first.

The Age of this computer will Govern what newer version of macOS it will Qualify to install. Use About this Mac from the Apple Icon on Desktop - the required Information will be there.

With the above information in-hand - follow this How to get old versions of macOS and verify what version this computer Qualifies to install.  For Best results use Safari to commence the download as Others may not work.

Safari will open a redirect and open the Apple Store where the download can commence.

Use Safari to download macOS on your Mac

Safari uses these links to find the old installers in the App Store. After you download the installer from the App Store, the installer opens automatically.

• macOS Big Sur can upgrade Catalina, Mojave, High Sierra, Sierra, El Capitan, Yosemite, Mavericks
• macOS Catalina can upgrade Mojave, High Sierra, Sierra, El Capitan, Yosemite, Mavericks
• macOS Mojave can upgrade High Sierra, Sierra, El Capitan, Yosemite, Mavericks, Mountain Lion
• macOS High Sierra can upgrade Sierra, El Capitan, Yosemite, Mavericks, Mountain Lion

Computer Qualify for the Monterey upgrade

macOS Big Sur 11 hardware requirements

macOS Catalina 10.15 hardware requirements

macOS Mojave 10.14 hardware requirements

macOS High Sierra 10.13 hardware requirements

macOS Sierra 10.12 hardware requirements

Caution - jumping over all the newer versions and directly to Big Sur  / Monterey on Qualifying computers is Technically possible - there are those who have attempted and were successful. Then there are those who attempted and had less than good results.

If this is a Production or Mission Critical Set-up - a more prudent and measure approach is suggested. 

The above is from observations on the Apple Support Community Forums and IMHO

Tips Big Sir Upgrade Released Nov 2020

Tips Monterey Upgrade  Released Oct 25, 2021

Make Time Machine Backup  is very useful and can be used to Revert to Previous Working macOS

Notation - Mojave is the Last version to support 32 bit applications / extensions and Drivers. Catalina, Big Sur & Monterey supports only 64 bit and there is no workaround.

Suggest using Go64 to find 32 bit application before attempting the upGrade. Some or many of the Application already installed may required update or upGrades to 64 Bit Versions.

It would appear that from a Mac running El Capitan clicking on the installers from High Sierra or newer in the link above called How To Get Old Versions...etc does not take you to the Mac App Store but instead a page called Mac App Store Preview with no option to download the installer.

To get to the Mac App Store from this page click on the Apple Inc. at the top of the page

To get to this

Now delete the" https" at the beginning and replace it with " macappstore" to get this

Now click return and it should take you to the Mac App Store to download Mojave

Note that the above has been done on a Mac early 2009 running El Capitan which cannot be upgraded any further.

The steps above are for Mojave, but should be the same for the later OSs, although the advice from others above are to upgrade to Mojave first.

I saw the workaround for deleting https and adding macappstore from a recent post so if this works then credit should go to Niel.

https://discussions.apple.com/thread/253663437

In this link go to # 3 and click on it. it will open the OS download in the App Store.How to upgrade to macOS Monterey - Apple Support I would still start with Mojave though as some are having problems when going from El Capitan to Big Sur or Monterey. In (How to get old versions of MacOS) scrolling towards the bottom and clicking on one of those links will do the same thing and you end up in the App Store. Are you saying that none of that redirects to the App Store?

Go to the App Store an in search type macOS Monterey and when you see thd update click on Get button and follow all steps to start thd update if from the App Store doesn’t work go to iTunes and type macOS Monterey in search

note: if macOS Monterey isn’t compatible for your Mac then type macOS Big Sur

.