installing Apache Open Office

I am running Imac on MacOS Catalina 10.15.7 (the device is too old to get more recent update, but it works fine so I want to use it).

I want to install Apache Open Office, version suitable for MacOs >=10.7.

I have downloaded the app from the apache site (since the Appstore doesn't want to list it), I can install it but can not run it, since the system blocks it because not downloaded from the Appstore...

How can I bypass this check?