Suppose you try to debug a ruby 2.7 program in VS Code using the ruby extension and get this error

Debugger terminal error: Process failed: spawn rdebug-ide ENOENT

Install some gems, ruby-debug-ide and debase

gem install ruby-debug-ide
gem install debase

Go to edit launch.json in the directory containing the file you're debugging. I found the program attribute had to be edited.

    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit:
    "version": "0.2.0",
    "configurations": [
            "name": "Ruby: Local File",
            "type": "Ruby",
            "request": "launch",
            "program": "${file}"

Now change to a tab with a ruby file open and press F5, the debugger should run the file successfully!