Minimum System Requirements - Powerlevel9k/powerlevel9k GitHub Wiki
Powerlevel9k is build around some advanced features of ZSH and a lot of other tools. It is the nature of things, that all software evolves and old features get deprecated. That is why we need minimum versions of such software.
ZSH
This is obviously the most used software in P9K. The minimum supported Version is ZSH 5.1