Unable to download Lightroom Classic 13.

This is a great argument (as if you need one) for making backups. Use Apple Time Machine for maximum convenience. If you had done that (maybe you have done that but did not think about it?), then you could have used Apple Migration Assistant to fully restore the new disk from a backup.

Did you at least make catalog backups if you did not make full disk backups? If not, then you have another problem and Adobe can’t help you with that one…

Thank you for your helpful and important replies. Is there a specific support email address for this type of request? Thank you. 

People report that if you contact Adobe support and ask for LrC 13, they will send you a link to download it. People also report that sometimes you have to be persistent and contact Adobe support multiple times until you find an agent who understands and knows how to provide the download link.

Just for background, current Adobe policy is to provide only the last two major versions of a Creative Cloud app for installation. This means every year when they release a major new version, the oldest one is dropped from support. This year we can install Lightroom Classic 15 and 14, next autumn it will probably shift up to Lightroom Classic 16 and 15. 

Link to the policy:

Creative Cloud Support Policy

Yes, it’s inconvenient, because using Creative Cloud means we have to budget to be able to keep our hardware relatively recent, and that is not easy for everyone. 

You might try contacting Adobe customer support directly if you need access to something that isn’t available to us in the general public. (This is mostly a user-to-user forum)