If you want to promote usage of real CPC computers, you can detect CPC emulators by:
*Checking if the memory is initialized with zeroes, as real machines have random memory values at boot. [https://www.cpc-power.com/index.php?page=detail&num=3905 The Eternal Light] homebrew doesn't work on real machine because of this.
*Focusing on the minute details in Z80, CRTC and PPI chips. They are most often wrong in emulators
*Examining the FDC chip. It is only replicated more or less superficially in all emulators because the internals of the chip are still unknown