Go to GitHub - platformio/platform-espressif32: Espressif 32: development platform for PlatformIO → Select wanted tag in the upper left corner → open platform.json → check version tag of the framework-arduinoespressif32 package (or whatever other version you’re interested in).
E.g.
→ Arduino-ESP32 2.0.6.
Or for platform-espressif32
→ Arduino-ESP32 2.0.4.
An upgrade of the version is also always mentioned in the release notes.