I don't know whether it's the best solution, but It worked for me: https://medium.com/@sergey-pekar/how-to-fix-annoying-xcode-26-not-building-swiftui-previews-error-cannot-execute-tool-metal-due-49564e20357c

Problem not solved (I forgot that I did a manual change in the Archived package): To allow uploading to the Appstore, I had to remove the CFBundleExecutable key in the help package Info.plist before submitting. Then it works. But if I don't remove this key, uploading ends with the same error, whatever I use Custom or Test Flight & App Store setting for upload.