Of course the (good) problem with C# is that it's moving so fast, articles like these can quickly become out of date.
* https://devblogs.microsoft.com/dotnet/
* https://devblogs.microsoft.com/visualstudio/
* https://devblogs.microsoft.com/dotnet/author/toub/ (for perf improvements by .NET version)
* https://dotnet.microsoft.com/en-us/apps/aspnet (of course!)
But it takes a while to catch-up if you are not keeping up-to-date on what is happening or coding in C#/.NET on a day-to-day basis
It is preferred to propagate correct type nullability instead :)