If you’re seeing the same error duplicated across all targets in Xcode 14 or newer, even though only one target is active, here’s the actual fix:

Go to Xcode > Settings > General, and under the “Issues” section and disable “Show live issues”.

This setting is responsible for scanning and reporting issues from all targets in your project or workspace, regardless of which one is currently selected. That includes static analysis, preprocessor errors, and undeclared identifiers – all duplicated for each target that includes the source file.

Tested and confirmed to resolve the issue.