Graphisoft is working on the web site / links... in the meantime...
The full information is in the PDF that is installed on your system. You can access it from the Help menu... or just directly from your ArchiCAD 18 Documentation folder as seen in the attached.
Library auto-migration is one useful step... but you'll see that there are other steps to consider. The Migrate-from-17 chapter includes:
Migrating from ArchiCAD 17
Migration of Rendering/Surface Settings to CineRender
Migration of Lights and Lamp Settings
Display of Elements in Interior Elevations
Collision Detection Checkbox for Building Materials
Images from QuickTime Formats
Visualization of Transparent Elements
Migrating EcoDesigner or Energy Evaluation Data
Migrating Libraries to ArchiCAD 18
Migrating a Teamwork Project (v. 13, 14, 15, 16 or 17) to ArchiCAD 18
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AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB