Is there a link where we can download macOSCatalina?

Yes, there is:

How to get old versions of macOS - Apple Support

Scroll down to "Use Safari to download macOS on your Mac" ... and use Safari, not Firefox or other browsers.

I've tried that link, and the Catalina Link is pointing to Monterey. I believe whoever made the page put the wrong link.

EDIT: I found the link:

https://apps.apple.com/us/app/macos-catalina/id1466841314?Mt=12