Microsoft only supports the current Office 2021 for Mac (single-purchase), or current Microsoft 365 applications (subscription) on macOS Monterey, Ventura, and Sonoma. In Fall 2024, Microsoft will drop support for Monterey, so even if you installed Office 2021 for Mac today, you would receive no further updates to it next Fall on Monterey.
Although you can Google Stack Social and find a current Office 2021 for Mac home and business suite for around $30, it might make more sense to obtain a very good Microsoft Office clone (Softmaker Office 2024) that avoids Microsoft's planned obsolescence with their three-year operating system support window.
And there is the free LibreOffice Suite, also a Microsoft Office clone.