I tested both options separately. Both worked. I really appreciate the rapid response. Sincere thanks.

It seems that the problem reaches into #Preview also - since #Preview seems to depend on the same missing libraries. I'm backing out of 16.4 for now, returning to 16.3 with its own set of problems - but at least I can simulate and preview. Following up - and now back on Xcode 16.3 - including iOS 18.5 in the simulator: This works out really well as I can now #Preview, and simulate(iOS 18.5) without crashes, and build for TestFlight and deployment. I'll wait awhile before I burn more hours trying to get Xcode 16.4 to behave.