Office 2019

It will work with 10.14.6. See the following from Microsoft: https://support.microsoft.com/en-us/office/upgrade-macos-to-continue-receiving-microsoft-365-and-office-for-mac-updates-16b8414f-08ec-4b24-8c91-10a918f649f8?ui=en-us&rs=en-us&ad=us

From Microsoft's site:

To provide you with the best experience, Office for Mac supports the three most recent versions of Apple's macOS. With the release of macOS 10.15 Catalina, Microsoft 365 for Mac and Office 2019 for Mac support macOS 10.15, 10.14, and 10.13*.

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

Meaning, it will run in 10.14.x. There's no need to upgrade the OS if you don't want to.

I am running Office 2019 bought two years ago under Mojave with no issues.