Getting "Unable to configure Firebase App : unrecognized selector sent to instance" on IOS
Solution 1:
I post my solution under your question although I'm not sure if it fits to your problem. One month later you probably found another way. But maybe others will find it helpful.
I had a similar error when trying to add Firebase Dynamic Links.
*** Terminating app due to uncaught exception'NSInvalidArgumentException',
reason: '-[__NSCFString count]:
unrecognized selector sent to instance 0x2823640c0'
terminating with uncaught exception of type NSException
The debugging halted in function
FIRDLAddToAllowListForCustomDomainsArray
The problem is the key FirebaseDynamicLinksCustomDomains in the Info.plist. It needs to be an array of Strings, not just a String.