Unable to debug external processes

I confirmed the problem with the debugger for Unity. (`unity.unity-debug`) The extension had two problems on Flatpak:
1. Mono is not available via `PATH`.
2. Cannot enumerate external processes.

1 can be easily solved by adding yet another SDK to `code.sh`. The question is how to resolve 2. I suspect any other debugger attaching to existing processes has the same issue and adding the permission for that operation will be beneficial for them, but that can also effectively disable the sandbox.