Adobe generally supports the current major release and the one immediately prior (the "N-1" policy). Because After Effects 2020 is now considered a legacy version (older than N-1 as of April 2026), it may not appear by default. Instal older version of After Effects - Adobe Community

To download (version 17.x) for Mac, you must use the official Adobe Creative Cloud Desktop app. How to Download the 2020 Version