What software needs to be updated?

No the operating system is fine. As Demo states above, it is an iTunes update. I recently updated my iPad, and I was promoted to do the same update. It appeared to be a small download, but the iPad was recognized after the requested update completed.

On you Mac, you need to ensure that iTunes or Funder (as appropriate for the installed version of macOS) is updated to the current version.

No. I am currently running 10.11.6 which is El Capitan and I am syncing just fine with iOS 14. Look at my post above. I think it’s an update to iTunes that you have to download. See my screenshot a above.

If this is what you are seeing on your Mac when connecting your iOS devices to iTunes, it is a minor update to iTunes that you need to download and install.