ArcObjects SDK 10.8 is not available as a public standalone download. Because it is part of the retired ArcGIS Desktop product line, you must access it through official Esri licensing portals. Geographic Information Systems Stack Exchange How to Access the SDK My Esri Portal : Log in to the My Esri Customer Service portal using a registered global account. Navigate to My Organizations
John searched online for the ArcObjects SDK 10.8 download link, but it seemed like it was nowhere to be found. He tried searching on the Esri website, but it seemed like he needed to have an account and a specific license to access the SDK. arcobjects sdk 108 download full