Hi. I was researching this issue as I'm catching up on MacOS for my iMac. Thanks adamjhoward for the 10.5.1.! I realized that the last version that works for my iMac MacOS (the last one possible is Catalina) is 10.6. Except I"m stuck now and have the same problem that I can't download 10.6 from the App Store. It only has 10.7.
Will the same trick with backing up Logic Pro X 10.5.1 and reload from App store work to get 10.6? Alternatively, would anyone have a backup of 10.6 that they would be willing to share?
Thanks,
Ed