Once the download starts, you can cancel it. The app is now "linked" to your account.
If you cannot get the legacy version to work or need to manage devices from a Windows PC, consider professional alternatives: download older version of apple configurator 2
Apple has a "Last Compatible Version" feature hidden in the Mac App Store. If you have ever "purchased" (downloaded) Apple Configurator 2 in the past with your Apple ID, follow these steps: on your older Mac. Sign in with the Apple ID you used previously. Once the download starts, you can cancel it