Can Microsoft Office be installed on Mac running macOS Catalina 10.15.7?

This should work ...

Assumptions: 1) you have a Microsoft Account and 2) there is no previous version of MS Office apps on your Mac.

• Go to Update history for Office for Mac
• Scroll down to October 11, 2022 16.66 (22100900) - This is the final build of MS365 that was compatible with macOS Catalina
• On that line, click on "Office Suite (without Teams)" to download the installer.
• After the download completes, run the installer
• After the install is complete, sign into your MS 365 account.
  • FYI it's been awhile since I did this and I do not recall if the installler has you sign in to your MS 365 account as part of the install ... or if it only installs the apps in which case you would just open one of the apps (e.g. Word) and sign in there.

First installs of MS 365 include 1-month free. If you want to use it beyond 1 month then you need to purchase an MS 365 subscription in order to continue using the Office apps.

Also note that there are no updates for MS 365 on Catalina. MS only supports & provides updates on the most recent 3 versions of macOS (currently Tahoe, Sequoia & Sonoma).

Microsoft only supports the current release of macOS (Tahoe) and the previous two releases (Sequoia, Sonoma) for new installations of Microsoft Office. You will be blocked by Microsoft if attempting to install Microsoft Office on Catalina.

Matti Haveri's recommendation for the free LibreOffice 25.8.* would still open your existing Microsoft documents and allow you to create new documents on Catalina.

There is also ample PDF documentation available for LIbreOffice that is written with LibreOffice Writer. This can help in flattening the learning curve. At this time, the PDF documentation is at 25.2 — and that is good enough. It will be updated over time.

The newest LibreOffice 25.8 runs on Catalina so try it (make sure to choose "macOS Intel" version when downloading).

https://www.libreoffice.org/download/download-libreoffice/

I should also mention SoftMaker's FreeOffice which is exactly that, and is an MS Office clone with a familiar interface, document compatibility, and is supported on macOS Mojave and later. Easier learning curve than LibreOffice.