Last checked on 4:39:24 PM July 18, 2020 GMT. Available and working on mainstream vscode builds.
Pop!_OS 20.04 LTS
It seems like platformio-vscode-ide depends on some extension called
ms-vscode.cpptool which is not available in the OSS version, but only in the proprietary Microsoft release. This is very unfortunate and should be resolved so Code OSS users can install PlatformIO.