pio platform uninstall [PLATFORM...]
# uninstall specific platform version using Semantic Versioning
pio platform uninstall PLATFORM@X.Y.Z
Uninstall specified Development Platforms
> pio platform uninstall atmelavr
Uninstalling platform atmelavr @ 0.0.0: [OK]
Uninstalling package tool-scons @ 2.4.1: [OK]
Uninstalling package toolchain-atmelavr @ 1.40801.0: [OK]
The platform 'atmelavr' has been successfully uninstalled!