Some of these tools are paid assets and will be marked with a 💸 emoji. This is not a paid endorsement, I use them myself.
I recommend https://github.com/zigurous/unity-cc0textures-importer which lets you import materials from ambientcg.com, a repository of Public Domain materials for Physically Based Rendering available under the Creative Commons CC0 1.0 Universal License.
💸 I recommend Jetbrains Rider for UdonSharp and Editor Scripting, due to its tight integration with Unity workflow combined with Jetbrains' signature refactoring tools. See: https://www.jetbrains.com/rider/buy/#personal
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