React Native linker command failed with exit code 1 with default app - ios

Question

I used React Native a few years back and am starting up using it again so I was just testing with the default app to check it builds ok in iOS. It runs ok in the simulator in xcode after opening the xcworkspace file but when selecting to build for release it fails with the classic linker error.
I noticed 'main.jsbundle' is red and thus missing from the project which I used to need to create but not sure if we still need to or how it is done? I checked the official documentation and there is a section for submitting to the play store...but no section about submitting to the Apple App store?? Can we not submit to the Apple store anymore?
The versions are:
"react": "16.8.6",
"react-native": "0.60.4",
I looked around for guides on submitting to the iOS store written by third parties but they are either a 1-2 years old or more or don't mention anything I haven't done. Again, no idea why there is no official documentation on iOS submission, unless it is harder to find than the Android one.
Error message in full:
Ld /Users/hasen/Library/Developer/Xcode/DerivedData/app-eeaxrfrnodznmfdedeoxgnyekkae/Build/Intermediates.noindex/app.build/Release-iphoneos/appTests.build/Objects-normal/arm64/appTests normal arm64 (in target: appTests)
cd /Volumes/Orchestra/Projects/reactnative/app/ios
export IPHONEOS_DEPLOYMENT_TARGET=9.0
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -arch arm64 -bundle -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS12.1.sdk -L/Users/hasen/Library/Developer/Xcode/DerivedData/app-eeaxrfrnodznmfdedeoxgnyekkae/Build/Products/Release-iphoneos -F/Users/hasen/Library/Developer/Xcode/DerivedData/app-eeaxrfrnodznmfdedeoxgnyekkae/Build/Products/Release-iphoneos -F/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/Library/Frameworks -filelist /Users/hasen/Library/Developer/Xcode/DerivedData/app-eeaxrfrnodznmfdedeoxgnyekkae/Build/Intermediates.noindex/app.build/Release-iphoneos/appTests.build/Objects-normal/arm64/appTests.LinkFileList -Xlinker -rpath -Xlinker #executable_path/Frameworks -Xlinker -rpath -Xlinker #loader_path/Frameworks -miphoneos-version-min=9.0 -dead_strip -bundle_loader /Users/hasen/Library/Developer/Xcode/DerivedData/app-eeaxrfrnodznmfdedeoxgnyekkae/Build/Products/Release-iphoneos/app.app/app -Xlinker -object_path_lto -Xlinker /Users/hasen/Library/Developer/Xcode/DerivedData/app-eeaxrfrnodznmfdedeoxgnyekkae/Build/Intermediates.noindex/app.build/Release-iphoneos/appTests.build/Objects-normal/arm64/appTests_lto.o -fobjc-arc -fobjc-link-runtime -ObjC -lc++ -lstdc++ -framework JavaScriptCore -framework XCTest -lPods-appTests -Xlinker -dependency_info -Xlinker /Users/hasen/Library/Developer/Xcode/DerivedData/app-eeaxrfrnodznmfdedeoxgnyekkae/Build/Intermediates.noindex/app.build/Release-iphoneos/appTests.build/Objects-normal/arm64/appTests_dependency_info.dat -o /Users/hasen/Library/Developer/Xcode/DerivedData/app-eeaxrfrnodznmfdedeoxgnyekkae/Build/Intermediates.noindex/app.build/Release-iphoneos/appTests.build/Objects-normal/arm64/appTests
Undefined symbols for architecture arm64:
"_RCTSetLogFunction", referenced from:
-[appTests testRendersWelcomeScreen] in appTests.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)