There is a *possibility* you may be able to install Office 365 on Monterey.
The final version that was compatible with Monterey was Office 365 v16.89.1 (Sep. 17, 2024). You should be able to download the installer from Microsoft's Update History For Office for Mac. Scroll down to the line for Sep. 17, 2024 version 16.89.1 and download the installer package for Office Suite with Teams or without Teams, whichever you prefer. You should then be able to install it.
Make sure you have Monterey 12.7.6 installed before you install this version of Office 365.
Note (this is the "possibility" piece). You will still need an Office 365 license to activate the installation. There is a 1-month free trial available, so you could sign up for the free trial and see if you can activate your installation. If it doesn't work you can cancel the subscription before the end of the 1-month trial.
Please let us know if this works!
(Full disclosure ... I have not done this myself, so I cannot claim that it works; only that it is a possibility.)