Can you give an example of where monkey patching made debugging hard? I have a decade of Ruby experience and can't think of a single time it was an issue

This is one of those things that sounds like it'd be a problem but it really isn't

If debugging is hard to you in Ruby because of monkey patching, it's an issue of not knowing the debugging tools. Attach pry or Ruby debug, and show the source location of a method, or log them. This isn't surprising - debugging Ruby is different to debugging most static languages, and more tutorials on how to do this well would be nice...

Also the use of monkey patching in Ruby peaked something like a decade and half ago. Outside of Rails, it's generally frowned on and introducing new methods is usually addressed by opting in by including modules these days.