The final release supporting the "non-CDB (non-Container Database)" architecture is "Oracle Database 19c" (B). Oracle deprecated the non-CDB architecture starting with 20c (never fully released) and mandated the multitenant architecture (CDB with PDBs) from 21c onward. 19c, as a long-term support release, was the last to support non-CDB databases, with Oracle recommending migration to multitenant in subsequent versions like 23c. Oracle's documentation confirms 19c as the end of non-CDB support.