So, I am not sure if this is the actual solution yet, but the error went away, when I did the following. Click on your project, go to General tab, at the bottom you have Frameworks, Libraries and Embedded Content, click on the + and add the FirabaseFirestore.

Interesting, I am just learning iOS, and during my courses I used Firebase but installed via CocoaPods, this time I added the package via add packages and when I want to use the Firestore DB to add in the app delegate also get this error, wonder what the issue could be. So the authentication features all work, but the Firestore seems to be missing for some reason. Will try and re install it later, but updating the package did not help. I am on Xcode 14.2 (14C18)