That depends on which HiveManager platform you are using, but this guide reviews all recommended firmware versions for all of our HiveOS model devices depending on which HiveManager platform is in use currently: https://thehivecommunity.aerohive.com/s/question/0D50c00007NeN2jCAF/hiveos-matrix
This guide will walk you through how to determine which HiveManager you are using, for reference: https://thehivecommunity.aerohive.com/s/article/Which-HiveManager-Platform-am-I-using
