Okay, good news, after trying several approaches I finally found a very simple fix/workaround... In the app build settings under Architecture, get rid of $(ARCHS\_STANDARD) (click the minus to delete it) and add both architectures as explicit values, arm64 and x86\_64. Apparently there's an issue with that default setting not really conveying that both architectures are needed when the package dependency is built, completely regardless of the "active architecture" setting. Everything works great with this change, I was able to build and notarize the app on M1 and verify it now also runs on x86.

Also a little more info - the package in question does have its Xcode project macOS target configured to build universal architecture and, for Release builds, build-active-architecture-only is set to NO. https://github.com/yahoojapan/SwiftyXMLParser

Solved: in the debugger output, Xcode warned about min and max sizes for toolbar items being deprecated. After changing all toolbar item sizes to "Automatic", the toolbar items appear again, and the issues with the Customize panel are fixed. Additionally, I was able to retain the existing separator-spacing of items by changing the toolbar type of the Window from "Automatic" to "Expanded".

Just posting a follow-up here, I did eventually decide to jettison the use of SKTexture because of this issue - there does not appear to be any workaround. Using the other init method of GKNoiseMap() that just takes noise, size, origin, sampleCount and seamless params, using noisemap.value() to get the generative values and using my own drawing code (supporting NSColors with alphas in the gradients I calculate) to render the output. It's slower so far (will be working on optimization) but the lack of alpha support in the SKTexture output was a deal-breaker. On the plus side, I can also now generate noise with more than two colors across the -1.0 to 1.0 value output; SKTexture only supported two opaque colors.

I'm just adding a reply to bump the question, ridged noise seems broken to me too - I can't get any results like that shown in the documentation (the lightning-style branching). I've tried all combinations of frequency, octave count and lacunarity, and the result ranges from something like particle board texture to fine pixel static.