Useful or not, from you.
platformio-vscode-ide Platformio extension missing from Vscodium and code-oss

Last checked on 4:39:24 PM July 18, 2020 GMT. Available and working on mainstream vscode builds.

Pop!_OS 20.04 LTS

That's a useful answer
Without any help

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.