Downloading for Mac can be tricky because Adobe typically only offers the current version and one major version prior through its standard installer.
Since InDesign 2020 (v15) is now several generations old, it is no longer directly listed in the Adobe Creative Cloud desktop app for standard users. (MAC) Adobe InDesign 2020 Free Download
Choose a plan (Individual or Student/Teacher) and enter your email. Downloading for Mac can be tricky because Adobe
You must cancel before the 7th day to avoid being charged. Option 2: Accessing Older Versions (Creative Cloud) (MAC) Adobe InDesign 2020 Free Download