iPod touch 2nd Generation (MC Model)

I am completely new to jailbreaking and found an old iPod touch 2nd Gen (MC Model) currently running on 4.2.1. I watched a couple YouTube videos on how to jailbreak it but they both said to use GreenPoision. I can't use GP though because my Mac is running Tahoe 26.2. Does anyone have any recommendations on what I should do to be able to jailbreak my iPod? Thanks