Compatibility of Office 24 with MacBook Air running 10.15.7

Microsoft Support – Office suites for individuals and families

"Office for Mac is supported on the three most recent versions of macOS. As new major versions of macOS are made generally" (text cuts off there)

Microsoft Support – Upgrade macOS to continue receiving Microsoft 365 and Office for Mac updates

"Note: As new major versions of macOS are made generally available, Microsoft will remove support for the oldest major version and support the newest and previous two major versions of macOS."

So Office 2024 was never supported on Catalina (which fell out of the "most recent three" long before Office 2024 came out). It was supported on Ventura, but Microsoft will be removing support there soon, if they haven't already.

FYI: No supported version of office will run on any version of macOS older than macOS 14 Sonoma.

You may be able to use the web based version of office.

FYI, the current version of LibreOffice (a free office suite that can work with many Office/365 files) will run on Catalina.

As for the Web-based Microsoft Office applications that KiltedTim mentioned, see:

Microsoft | Microsoft 365 – Use Microsoft 365 apps for free on the web

You need to have an Internet connection when using these. If Catalina's version of Safari has problems with them, you could try accessing them using Firefox. (The current version of that browser will run on Catalina.)

No.