Visual Studio 2022 (17.12.0) makes it look like the "field" keyword is usable. But it is only usable if you set the language version to "preview".
Note: this is specifically related to Visual Studio 2022 version 17.12.0 and .NET 9.0.100. I will keep an eye on future versions.
Quick Fix:
Set <LangVersion>preview</LangVersion> in the project settings.