Monterey support on 2015 imac 27”

Apple supports the current release and the previous two releases of macOS. With Sequoia's release on Sept 16, Monterey will drop off the supported list. Apple at its discretion may issue subsequent bug fixes or security releases for Monterey, but no new features will arrive and the Safari browser is unlikely to receive further updates.

Microsoft follows Apple's support schedule so if you are a current user of Microsoft 365/Office 2021 for Mac, you can continue to use the product but no further updates will be provided after Microsoft switches to the Ventura as the minimum operating system supported this Fall.

Your iMac is not supported by Ventura or later operating systems.

There are the iMac compatible with macOS iMac

Identify your iMac

• iMac (24-inch, M1, 2021)
• iMac (Retina 5K, 27-inch, 2020)
• iMac (Retina 5K, 27-inch, 2019)
• iMac (Retina 4K, 21.5-inch, 2019)
• iMac (Retina 5K, 27-inch, 2017)
• iMac (Retina 4K, 21.5-inch, 2017)
• iMac (21.5-inch, 2017)
• iMac (Retina 5K, 27-inch, Late 2015)
• iMac (Retina 4K, 21.5-inch, Late 2015)
• iMac (21.5-inch, Late 2015)