GNU Guitar is a guitar effects processor, much like Guitarix and Rakarrack.

It was started about ten years ago, formally known as GNUitar. Over the last year, it has been refactored (and some parts completely rewritten) to use modern software technologies. It's cross-platform, so it runs on Linux systems and Windows (macOS is on the to-do list).

Here's a link to the change summary: https://github.com/gnu-guitar/gnu-guitar/releases/tag/v0.4.0-alpha

The project is in it's infancy still. Let me know if you're interested in contributing!