Just ran across this on a project that is being refactored to have "better" code structure. This inability to preview views within a package that depend upon another package is pretty surprising, given the push toward Packages, the age of this post, and the number of upvotes here.
In my experience, it's not that it couldn't find the package—adding the full path to the package ("/my/specific/dir/PackageName" instead of "../PackageName") did not work.
The project builds and runs fine for simulators and the automated tests run and pass, but it does not build for previews.
I sometimes see crashes, and sometimes the inline xcode source code error "could not find module '' for target 'x86_64-apple-ios-simulator'; found: arm64, arm64-apple-ios-simulator".
Those details seem interesting (not available for x86 when running simulator)—is this what others are seeing? I've tried setting various architectures—my Mac, my Mac (catalyst), iOS simulator running iOS15, etc.
For now, my workaround may be to not have packages that depend upon each other, which partly defeats the purpose. And I may file a bug report, but I may find existing and upvote.