Freeware - APU Loudness Meter VST Plugin

https://apu.software/meter/

The APU Loudness Meter plug-in is a free dynamic range analysis tool supporting a variety of loudness types (LUFS, True Peak, RMS, Peak). View changes to your audio’s loudness in real-time or get a bigger-picture look with configurable history and histogram views. View both real-time and accumulated statistical information all from one screen.