Fitbit OS 5.2.1 update for Versa 3 & Sense provides little-to-no bugfixes
How to Update Fitbit Firmware - YouTube
A Comprehensive Guide to Fitbit Sense & Versa 3: A simple Approach to Master your Fitbit Sense & Versa 3 with 2021 Latest Fitbit Firmware Hidden Features & Troubleshooting Common Problems :
Latest Firmware Update Fitbit Versa 2/Versa Lite Edition - YouTube