Left is with Adaptive Battery on, the right is with adaptive battery off. Thrilled that I've managed to fix things a little, thank to Reddit! : r/GalaxyS9
Android 9.0+ and Fitbit: Adaptive Battery Issues | by Alex Bucknall | Medium
Here Are Five Ways To Optimise Your Samsung Galaxy Z Flip 4's Battery Life - Lowyat.NET
Galaxy S21/Ultra/Plus: How to Enable/Disable Adaptive Battery - YouTube
Android Adaptive Battery: Everything you need to know - Android Authority
What is Android Adaptive Battery: Everything you need to know