The following code in NeCoreAppSettings can't convert to a
var values = config.GetChildren().Map(x => x.Value);
Unfortunately we were using MyGet in our CI/CD and experienced the error, while it was working fine on localhost, as it for some reason was using an older assembly.
I've prevented it from trying to convert a list to a dictionary in this commit.
This change is available from the latest v5.4.1 that's now available on MyGet.
Thank you, that solves it