older version Adobe InDesign

Do you have a paid Creative Cloud plan?  I ask because legacy Creative Suite software is no longer sold legally by any vendor or retailer in any country.

Adobe expects Creative Cloud users to have the latest software no more than 2 versions back -- mac Mojave, Catalina, Big Sur.

El Capitan is not supported anymore.  Sorry.
- https://helpx.adobe.com/creative-cloud/system-requirements.html

Direct Download Links https://prodesigntools.com/tag/ddl MAY help
-you MUST do what it says in Note: Very Important Instructions
-https://prodesigntools.com/adobe-cc-2015-direct-download-links.html#download-instructions
-the prodesign links go directly to Adobe's file server, so this process
--will only work until Adobe completely removes the old version(s) from the server
.
When you do have a download, be sure to copy it to AT LEAST one external device
-since Adobe does sometimes remove old versions from the server
-a usb flash drive or hard drive, or write to a DVD