Linker errors in Xamarin Forms iOS

Question

I am getting below linker errors upon build in an Xamrain Forms iOS project. I have tried from both a Visual Studio for Mac and from Visual Studio Windows paired with a Mac.

I have referenced as many Xamarin.Firebase.iOS.* assemblies as I can see as relevant but no luck.

What am I doing wrong?

Thanks

Regards

Native linking failed, undefined symbol: _GULLogWarning. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined symbol: _pb_encode_varint. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined Objective-C class: GULNetwork. The symbol '_OBJC_CLASS_$_GULNetwork' could not be found in any of the libraries or frameworks linked with your application.
Native linking failed, undefined symbol: _GULLogBasic. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
] in GoogleAppMeasurement(APMMeasurement.o)
Native linking failed, undefined symbol: _kGULNetworkHTTPStatusOK. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined symbol: _pb_encode_submessage. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined symbol: _kGULNetworkHTTPStatusCodeNotFound. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined symbol: _pb_encode_string. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined symbol: _kGULNetworkHTTPStatusCodeCannotAcceptTraffic. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined Objective-C class: GULAppEnvironmentUtil. The symbol '_OBJC_CLASS_$_GULAppEnvironmentUtil' could not be found in any of the libraries or frameworks linked with your application.
Native linking failed, undefined symbol: _GULSetLoggerLevel. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined symbol: _pb_ostream_from_buffer. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
] in GoogleAppMeasurement(APMMeasurement.o)
Native linking failed, undefined Objective-C class: GULMutableDictionary. The symbol '_OBJC_CLASS_$_GULMutableDictionary' could not be found in any of the libraries or frameworks linked with your application.
Native linking failed, undefined Objective-C class: GULAppDelegateSwizzler. The symbol '_OBJC_CLASS_$_GULAppDelegateSwizzler' could not be found in any of the libraries or frameworks linked with your application.
Native linking failed, undefined symbol: _pb_istream_from_buffer. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined symbol: _pb_read. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined symbol: _kGULNetworkHTTPStatusCodeUnavailable. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
] in GoogleAppMeasurement(APMMeasurement.o)
Native linking failed, undefined Objective-C class: GULSwizzler. The symbol '_OBJC_CLASS_$_GULSwizzler' could not be found in any of the libraries or frameworks linked with your application.
Native linking failed, undefined symbol: _pb_decode_varint. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined symbol: _GULIsLoggableLevel. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined symbol: _pb_encode. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed. Please review the build log and the user flags provided to gcc: -ObjC -lc++ -lsqlite3 -lz
Native linking failed, undefined symbol: _pb_decode. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined symbol: _GULLog. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined symbol: _pb_encode_tag_for_field. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined symbol: _kGULNetworkHTTPStatusNoContent. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
] in GoogleAppMeasurement(APMMeasurement.o)
linker command failed with exit code 1 (use -v to see invocation)
Native linking failed, undefined symbol: _GULLogInfo. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed, undefined symbol: _kGULNetworkHTTPStatusCodeNotModified. Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.