You can also target the minute details of the Z80, CRTC and PPI chips that are almost always wrongly implemented by emulators.
And you can target the FDC chip that is only replicated more or less superficially in all emulators because the internals of the chip are still unknown.
By combining multiple detection methods, you can definitely attain a 100% success rate of detecting all emulators, even the toughest ones.