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Cables[0] is pretty cool too. Kirell Benzi has released some impressive work using it [1].

Had a look in Mint's software manager and found this (flatpak/aur/macports/windows): https://github.com/fralonra/wgshadertoy

There's also bonzomatic which the demo scene uses for shader live coding competitions:

Also on macOS (and iPadOS) it's super easy to get started with Metal shaders in Playgrounds.

For swiftUI+metal specifically: https://metal.graphics

Godot has a shader editor and the effects are updated in real time; another option.