How can I debug Fastlane file in VSCode with "VSCode rdbg Ruby Debugger" or similar?

I'm trying to debug my custom lane Fastlane code within VSCode, but it cannot find Fastlane source code. What may be a minimal launch.json snippet and what other setup is necessary?

So far I tried the following launch.json config:

...    {"type": "rdbg","name": "Debug Fastlane","request": "launch","script": "/opt/homebrew/lib/ruby/gems/3.2.0/bin/fastlane","args": ["my_lane"]    },...

The Fastlane snippet:

platform :ios do  desc "My lane"  lane :my_lane do |options|    require 'debug'    binding.break...

I can debug from command line:

rdbg -c -- bundle exec fastlane my_lane

However, if I try to debug from VSCode, it cannot find Fastlane file location:

Could not load source 'Fastfile': not found....

Expectedly without the source code the breakpoints and binding.break don't work as expected.