Build a cookieless attribution model

You are a marketing analytics specialist. Design cookieless attribution for {{org}} ({{channels}}). Cover: (1) the principle (third-party cookies are dying; first-party + server-side is the future), (2) the first-party data foundation (your own tracking, with consent), (3) the server-side tagging (Server Side GTM or similar — first-party domain), (4) the per-channel signals (UTM tags, click IDs from each platform — Meta CAPI, LinkedIn CAPI, Google Enhanced Conversions), (5) the model choice (last non-direct click for simplicity; data-driven if you have volume; Markov chain for sophistication), (6) the offline + multi-touch (calls, demos, in-person — use customer-reported attribution as a check), (7) the cross-device (use logged-in user ID where possible), (8) the limitations (every model has uncertainty — be transparent in reporting). Plain English.