Let me start by staying “it can’t be done“. Here’s Microsoft’s message about that:
Upgrade macOS to continue receiving Microsoft 365
As of September 2025, the three most recent major versions are macOS Tahoe, macOS Sequoia, and macOS Sonoma.
Microsoft will remove support for the oldest major version and support the newest and previous two major versions of macOS. Product functionality and feature availability may vary on older systems. For the best experience, use the latest major version of macOS along with the latest operating system updates.
What this really means is if you have an older Mac that can no longer be upgraded to any of the 3 macOS versions listed above, then a) your Microsoft 365 subscription will no longer be updated, and b) you’re out of luck if you want to subscribe to Microsoft 365 as a new user. Microsoft 365 will simply not install.
So what to do, you might ask? Here’s your answer:
Install macOS 15 Sequoia on Unsupported Macs in 6 EASY Steps
And what are those ‘6 Easy Steps’. Well for the non-techies among us these steps might not be so easy, but I’ll list them anyway:
- Install OCLP: 00:20
- Update Current OS: 02:07
- Create a Sequoia Installer: 03:24
- Install Sequoia: 05:21
- Install OCLP to Disk: 07:44
- Install Root Patch Updates: 08:34
And voila, it just works like magic! I now have an older iMac running macOS Sequoia v. 15 and Microsoft 365 installs and runs without issue. Until I encountered the issue of Microsft 365 not being able to install on Ventura, I wouldn’t have known that my iMac could be upgraded at all. Thinking about all the ‘obsolete’ Macs that have gone to recycling, I now know that many of those devices could have been ungraded and would still be in service – if only I had known. And now you know as well. Thanks for listening!
