Xcode 26.4 - Old skip project - Missing preview error

Since I've updated to the latest Xcode (26.4) I'm not able to render SwiftUI Previews in Xcode. Every view I try to render have this very same error:

Missing Preview
Ensure preview is compiled for active scheme & destination
If the preview is excluded from the build it will be missing in the Xcode canvas. The file containing the preview must be compiled by the active scheme for your given destination. Check if the preview is filtered out by compile-time checks, dead code stripping, or other settings.

I've tried several projects created in the past few months, all of them have this issue. If I open the very same project on Xcode 26.3 previews works fine.

I've tried to create a new project with skip create, added the #Preview macro to the ContentView and it works. I then tried to compare the build settings on both projects and I didn't see any difference. Even tried to launch skip verify --fix on the old projects, but no luck.

Anybody else have this issue? Or any hint on where to look to try and fix it?

ps: here's the diagnostic report from the preview:

Diagnostic report.txt

Start with the attached Diagnostic report.txt and compare an affected older project with a newly created skip project in Xcode 26.4, then check the result of skip verify --fix. Reproduce the issue across the reported projects and compare against Xcode 26.3; done means SwiftUI previews render in the affected projects on Xcode 26.4.