: z/OS media is not freely available. Ensure compliance with IBM licensing agreements.
If you are looking for a mainframe environment to learn on without licensing hurdles, consider these alternatives: hercules z os 21 download link
IBM z/OS 2.1 emulator is technically possible but carries significant legal and technical hurdles. While Hercules can emulate the required 64-bit z/Architecture : z/OS media is not freely available
If you just want to see how a mainframe feels, you can download . This is a 1970s-era version of the IBM operating system that has entered the public domain. hercules z os 21 download link