Last week Microsoft released Entity Framework Core 3.0 Preview 7 and Entity Framework 6.3 Preview 7.
Entity Framework 6 (EF6) was first released in 2008 and runs on the .NET Framework 4.x (available only on Windows). Entity Framework Core (EF Core) is a complete cross-platform rewrite of EF6 that can run on .NET Core or .NET Framework. A detailed feature comparison between EF Core and EF6 can be found here.
The new previews were made available on the same day as .NET Core 3.0 Preview 7 and ASP.NET Core 3.0 Preview 7. The release schedule for EF Core is in-sync with the .NET Core release schedule.
Supporting EF6 on .NET Core is one of the major features for the EF6.3 release. With the release of Preview 7, the majority of the work related to this feature has been completed.
One of the major roadmap goals of EF Core 3.0 involves making profound changes in the existing LINQ implementation. Related updates in Preview 7 include support to SQL translation of LINQ set operators like Union, Concat, Intersect, and Except. The release also includes a new API for intercepting database operations (similarly to the interception feature in EF6). Intercepting database operations allow simple logic (interceptors) to be invoked before or after database operations happen (such as committing a transaction or opening a connection).
Other changes include the postponing of two major features, originally planned for EF Core 3.0: support for property bag entities and the ability to ignore parts of the model for migrations. Also, a list of breaking changes (changes that have the potential to break applications developed for EF Core 2.2.x) is being kept up-to-date on every preview.
EF Core 3.0 and EF6 are both distributed as NuGet packages. Given the rapid pace of development in EF Core 3.0, Microsoft recommends switching to the nightly build of Preview 8 to try fixes that are not included in Preview 7.