[mytydev]

The fiddler landing page says it runs on Windows, macOS, and Linux, so maybe give it another try.

[logicuce]

The original thing is now called Fiddler Classic and it is still Windows only. Not maintained anymore, sadly. It has first class scripting support.

[leptons]

I still use Fiddler Classic, at least once a week when I need to dig-in on a problem. It occasionally gets an update though I can't remember the last time it did.

It's so powerful, especially with the JScript scripting language. Such a powerful tool.