This is the most common. The crack attempts to reverse the algorithm that validates a product key.
Most users searching for "multi keyboard macros crack" don't just want the software for free; they want a specific technical limitation removed.
The 3 Biggest Macro Limitations in Trial Versions: multi keyboard macros crack
The "Fake Crack" Scam: Be aware that 90% of "MKM cracks" on YouTube or Pastebin are malware. Because MKM runs with high privileges (to read keystrokes), attackers love using it as a vector. A fake crack will not actually unlock macros; instead, it will install a keylogger (ironically, using the same macro engine) to steal your passwords.
If by "crack" you mean finding a way to use multi-keyboard macros effectively or bypassing limitations, here are a few: This is the most common
This is rare and dangerous. Instead of cracking the software, the user cracks the communication layer. A custom driver is installed that pretends to be a licensed version of MKM but actually forwards macro commands to an AutoHotkey (AHK) script.
Sample AutoHotkey approach (concept):
Because the keyboards are separated, you can create macros on Keyboard B that type into Keyboard A. This allows for Robotic Process Automation (RPA).